The Climate of the
United States
Front view of the Statue of Liberty
Climate Map
Climate map of the United States
What is the climate of the United States like?
The United States is the fourth largest country in the world. It borders Canada to the north and Mexico to the south. Alaska and the Hawaiian Islands are described on separate pages. The contiguous area of the "lower" 48 states lies between 25° and 49°N and lies entirely outside the tropics. It includes areas with a very wide range of weather and climate throughout the year. Occasionally, parts of the United States experience extremes of heat and cold typical of hot tropical deserts or frigid arctic regions. Another characteristic of the weather and climate of the United States is the weather variability over fairly short periods of time throughout all seasons.
The reason for these weather fluctuations is the belt of disturbed westerly winds that sweep the country. Most regions of the USA are affected by storms or depressions with the associated warm and cold fronts almost all year round. Most southwest winds bring clouds, rain (or snow) and disturbed, changeable weather. The central and northeastern parts of the US are particularly vulnerable to sudden temperature changes during such periods.
The central portion of the United States—the Great Plains—stretching from the Rockies in the west to the Appalachian Mountains in the east, is mostly flat and mostly below 2,000 feet (600 meters). This area is wide open to the influence of two very contrasting types of air masses. Cold polar and arctic air can flow south from Canada's Arctic regions, and warm, humid tropical air can flow north from the Caribbean and Gulf of Mexico. When one air mass replaces another, especially in winter and spring, the temperature can change by as much as 40° to 50°F (22° to 28°C) in a few hours. Such sudden changes can also occur in the northeast of the country (as far south as Virginia). Farther south on the Atlantic and Gulf coasts, temperature changes are less severe but can still produce a notable change in weather. On the Pacific Coast (west of the Rocky Mountains), the Pacific Ocean has a more even influence on the climate, with much less winter-to-summer or day-to-day temperature variation. The Rocky Mountains prevent this maritime influence from reaching the center of the country.
North America is a large continent, which also results in seasonal extremes of winter cold and summer heat. Only the Pacific coast and to a lesser extent the Gulf of Mexico coast and the Atlantic Ocean south of Virginia benefit from the sea's moderating effect on temperatures. Compared to Western European countries at the same latitude, the United States has greater temperature extremes and daily or weekly changes are much more evident. Central parts of the United States have a more extreme or continental climate than Central or Eastern Europe.
Some parts of the United States are subject to hurricanes and tornadoes, which can be particularly violent and destructive. Hurricanes hit the southeastern states bordering the Gulf of Mexico and the Atlantic Ocean once or twice most years. These tropical storms, which bring very strong winds and torrential rain, move northeast from the Caribbean region before dying off in the mid-Atlantic. A tornado, often referred to as a "whirlwind" or "twister" in the US, is a much more localized and destructive windstorm. Tornadoes can almost completely destroy buildings along a narrow path no more than a few hundred meters wide. They occur mainly in spring and summer on days when violent thunderstorms with rapid temperature changes occur along or near a cold front.
The western third of the United States is home to a series of high mountain ranges and plateaus collectively referred to as the Rocky Mountains or Western Cordilleras. The weather and climate vary greatly from place to place depending on the altitude. There are many high mountain ranges with peaks over 14,000 feet (4,250 m), extensive plateaus between 4,000 and 7,000 feet (1,200–2,000 m), and some small areas such as Death Valley in Southern California that lie below sea level. This results in a wide variety of climatic conditions with some very humid and snowy mountain regions and some semi-arid or even desert-like lowlands with large temperature extremes. In contrast, the climate of the central plains of the US, and to a lesser extent the Atlantic Seaboard, is much more uniform over large distances.
The United States can be divided into the following climatic regions: the northeastern states; the southern Atlantic states; the Midwest or northern interior; the southern interior and the Gulf states; the states of the Rocky Mountains regions; the states of the Pacific northwest; and California:
The Northeastern States (New England)
Including Maine, New Hampshire, Vermont, Massachusetts, Rhode Island, Connecticut, Delaware, New Jersey, Maryland, the eastern parts of the larger states of New York and Pennsylvania, and the District of Columbia (Washington DC).
This region can experience changeable weather throughout the year with moderate rainfall in all months. Winters in the north are wet and usually snowy, but summers south of New York tend to be slightly wetter. Summer heatwaves can produce temperatures in excess of 100°F (38°C) for a few days, and such hot spells are usually made more uncomfortable by high humidity levels on or near the coast. In the big cities of this region, urban heatwaves are even more uncomfortable as temperatures are often a few degrees higher than in more rural areas. From time to time, very cold spells can hit the entire region in winter or even spring, with very heavy snowfall likely in the north. The region includes the northern Appalachian Mountains, which range in elevation from 4,000 to 6,000 feet (1,200 to 1,800 m). Winters can be long and severe at these higher elevations, although there are many opportunities for winter sports. In the summer there are also resorts in the mountains that provide relief from the heat and humidity of the coast.
Although this is one of the less sunniest parts of the United States, it receives more year-round sunshine than most of Northwest Europe. Daily hours of sunshine in the coastal lowlands, averaging four to five in winter and up to nine or ten in summer. Locally, fog can reduce solar radiation on the coast both in summer and in winter. Some valleys in the Appalachian Mountains experience valley fog in winter.
Characteristic weather for this region is represented by the climate of Portland, Boston, and Washington.
| Climate data for Portland, Maine (1991–2020) | |||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Month | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | Year |
| Average high °F (°C) | 32.4 (0.2) | 35.0 (1.7) | 42.3 (5.7) | 53.8 (12.1) | 64.2 (17.9) | 73.6 (23.1) | 79.5 (26.4) | 78.7 (25.9) | 71.1 (21.7) | 59.5 (15.3) | 48.4 (9.1) | 38.3 (3.5) | 56.4 (13.6) |
| Daily mean °F (°C) | 24.0 (−4.4) | 26.2 (−3.2) | 34.1 (1.2) | 44.6 (7.0) | 54.9 (12.7) | 64.3 (17.9) | 70.4 (21.3) | 69.2 (20.7) | 61.6 (16.4) | 50.3 (10.2) | 40.0 (4.4) | 30.3 (−0.9) | 47.5 (8.6) |
| Average low °F (°C) | 15.6 (−9.1) | 17.3 (−8.2) | 26.0 (−3.3) | 35.4 (1.9) | 45.5 (7.5) | 55.0 (12.8) | 61.2 (16.2) | 59.7 (15.4) | 52.1 (11.2) | 41.0 (5.0) | 31.7 (−0.2) | 22.4 (−5.3) | 38.6 (3.7) |
| Average precipitation inches (mm) | 3.50 (89) | 3.54 (90) | 4.08 (104) | 4.41 (112) | 3.67 (93) | 4.15 (105) | 3.43 (87) | 3.57 (91) | 3.77 (96) | 5.25 (133) | 4.25 (108) | 4.50 (114) | 48.12 (1,222) |
| Average snowfall inches (cm) | 18.6 (47) | 16.6 (42) | 13.6 (35) | 2.8 (7.1) | 0.0 (0.0) | 0.0 (0.0) | 0.0 (0.0) | 0.0 (0.0) | 0.0 (0.0) | 0.2 (0.51) | 2.3 (5.8) | 14.6 (37) | 68.7 (174) |
| Source: NOAA | |||||||||||||
| Climate data for Boston, Massachusetts (1991−2020) | |||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Month | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | Year |
| Average high °F (°C) | 36.8 (2.7) | 39.0 (3.9) | 45.5 (7.5) | 56.4 (13.6) | 66.5 (19.2) | 76.2 (24.6) | 82.1 (27.8) | 80.4 (26.9) | 73.1 (22.8) | 62.1 (16.7) | 51.6 (10.9) | 42.2 (5.7) | 59.3 (15.2) |
| Daily mean °F (°C) | 29.9 (−1.2) | 31.8 (−0.1) | 38.3 (3.5) | 48.6 (9.2) | 58.4 (14.7) | 68.0 (20.0) | 74.1 (23.4) | 72.7 (22.6) | 65.6 (18.7) | 54.8 (12.7) | 44.7 (7.1) | 35.7 (2.1) | 51.9 (11.1) |
| Average low °F (°C) | 23.1 (−4.9) | 24.6 (−4.1) | 31.1 (−0.5) | 40.8 (4.9) | 50.3 (10.2) | 59.7 (15.4) | 66.0 (18.9) | 65.1 (18.4) | 58.2 (14.6) | 47.5 (8.6) | 37.9 (3.3) | 29.2 (−1.6) | 44.5 (6.9) |
| Average precipitation inches (mm) | 3.39 (86) | 3.21 (82) | 4.17 (106) | 3.63 (92) | 3.25 (83) | 3.89 (99) | 3.27 (83) | 3.23 (82) | 3.56 (90) | 4.03 (102) | 3.66 (93) | 4.30 (109) | 43.59 (1,107) |
| Average snowfall inches (cm) | 14.3 (36) | 14.4 (37) | 9.0 (23) | 1.6 (4.1) | 0.0 (0.0) | 0.0 (0.0) | 0.0 (0.0) | 0.0 (0.0) | 0.0 (0.0) | 0.2 (0.51) | 0.7 (1.8) | 9.0 (23) | 49.2 (125) |
| Source: NOAA | |||||||||||||
| Climate data for Washington D.C. (1991−2020) | |||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Month | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | Year |
| Average high °F (°C) | 44.8 (7.1) | 48.3 (9.1) | 56.5 (13.6) | 68.0 (20.0) | 76.5 (24.7) | 85.1 (29.5) | 89.6 (32.0) | 87.8 (31.0) | 80.7 (27.1) | 69.4 (20.8) | 58.2 (14.6) | 48.8 (9.3) | 67.8 (19.9) |
| Daily mean °F (°C) | 37.5 (3.1) | 40.0 (4.4) | 47.6 (8.7) | 58.2 (14.6) | 67.2 (19.6) | 76.3 (24.6) | 81.0 (27.2) | 79.4 (26.3) | 72.4 (22.4) | 60.8 (16.0) | 49.9 (9.9) | 41.7 (5.4) | 59.3 (15.2) |
| Average low °F (°C) | 30.1 (−1.1) | 31.8 (−0.1) | 38.6 (3.7) | 48.4 (9.1) | 58.0 (14.4) | 67.5 (19.7) | 72.4 (22.4) | 71.0 (21.7) | 64.1 (17.8) | 52.2 (11.2) | 41.6 (5.3) | 34.5 (1.4) | 50.9 (10.5) |
| Average precipitation inches (mm) | 2.86 (73) | 2.62 (67) | 3.50 (89) | 3.21 (82) | 3.94 (100) | 4.20 (107) | 4.33 (110) | 3.25 (83) | 3.93 (100) | 3.66 (93) | 2.91 (74) | 3.41 (87) | 41.82 (1,062) |
| Average snowfall inches (cm) | 4.9 (12) | 5.0 (13) | 2.0 (5.1) | 0.0 (0.0) | 0.0 (0.0) | 0.0 (0.0) | 0.0 (0.0) | 0.0 (0.0) | 0.0 (0.0) | 0.0 (0.0) | 0.1 (0.25) | 1.7 (4.3) | 13.7 (35) |
| Source: NOAA | |||||||||||||
The Southern Atlantic States
Including Florida, Georgia, North Carolina, South Carolina, Virginia, West Virginia.
Along the Atlantic coast, the temperature gradually increases towards the south, giving Florida an almost tropical climate. The greatest contrast can be seen in winter temperatures. Northern Virginia and much of West Virginia in the Appalachian Mountains have winter conditions more typical of the Northeastern region. Peak summer temperatures tend to be similar in the southern Atlantic states, but the summer season gets longer as you head south, and spring and fall are warmer. Florida has a very oceanic climate, heavily influenced by the surrounding warm Atlantic waters, so summers rarely experience the high temperatures sometimes measured as far north as New York. On the other hand, Florida and the coastal lowlands of Georgia and the Carolinas have mild winters, and frost and snow are much less common than in Maryland or Virginia. In northern Florida and southern Georgia, snow falls only once every ten or fifteen years, but in southern Virginia it falls most years.
The amount of precipitation that falls during the summer months increases towards the south and a significant portion of this is associated with thunderstorms. Florida has more thunderstorms than any other state in the US—over a hundred a year in parts of the state. This region is also hit by hurricanes or less severe tropical storms at least once or twice a year, which are responsible for some of the heavier rainfall during the months of July through October. This is the sunniest part of the eastern United States, averaging six hours of sunshine in the winter to nine or ten in the summer. Florida is particularly sunny in the winter, which combined with the much warmer temperatures at this time, makes it a popular winter destination. The summer months in Florida are slightly less sunny than in areas further north, as thunderclouds regularly form in the afternoon.
Characteristic weather for this region is represented by the climate of Richmond, Charleston, and Miami.
| Climate data for Richmond, Virginia (1991–2020) | |||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Month | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | Year |
| Average high °F (°C) | 47.8 (8.8) | 51.6 (10.9) | 59.6 (15.3) | 70.4 (21.3) | 77.8 (25.4) | 85.6 (29.8) | 89.5 (31.9) | 87.5 (30.8) | 81.2 (27.3) | 70.9 (21.6) | 60.4 (15.8) | 51.5 (10.8) | 69.5 (20.8) |
| Daily mean °F (°C) | 38.3 (3.5) | 41.0 (5.0) | 48.4 (9.1) | 58.4 (14.7) | 66.7 (19.3) | 75.0 (23.9) | 79.4 (26.3) | 77.5 (25.3) | 71.2 (21.8) | 60.0 (15.6) | 49.6 (9.8) | 41.8 (5.4) | 58.9 (14.9) |
| Average low °F (°C) | 28.8 (−1.8) | 30.4 (−0.9) | 37.2 (2.9) | 46.4 (8.0) | 55.7 (13.2) | 64.5 (18.1) | 69.2 (20.7) | 67.6 (19.8) | 61.1 (16.2) | 49.0 (9.4) | 38.8 (3.8) | 32.1 (0.1) | 48.4 (9.1) |
| Average precipitation inches (mm) | 3.23 (82) | 2.61 (66) | 4.00 (102) | 3.18 (81) | 4.00 (102) | 4.64 (118) | 4.37 (111) | 4.90 (124) | 4.61 (117) | 3.39 (86) | 3.06 (78) | 3.51 (89) | 45.50 (1,156) |
| Average snowfall inches (cm) | 3.7 (9.4) | 2.2 (5.6) | 1.1 (2.8) | 0.0 (0.0) | 0.0 (0.0) | 0.0 (0.0) | 0.0 (0.0) | 0.0 (0.0) | 0.0 (0.0) | 0.0 (0.0) | 0.0 (0.0) | 1.8 (4.6) | 8.8 (22) |
| Source: NOAA | |||||||||||||
| Climate data for Charleston, South Carolina (1991–2020) | |||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Month | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | Year |
| Average high °F (°C) | 58.0 (14.4) | 60.3 (15.7) | 65.6 (18.7) | 72.3 (22.4) | 79.0 (26.1) | 84.3 (29.1) | 87.5 (30.8) | 86.4 (30.2) | 82.6 (28.1) | 75.6 (24.2) | 67.1 (19.5) | 60.9 (16.1) | 73.3 (22.9) |
| Daily mean °F (°C) | 50.8 (10.4) | 53.2 (11.8) | 58.8 (14.9) | 66.0 (18.9) | 73.5 (23.1) | 79.2 (26.2) | 82.3 (27.9) | 81.4 (27.4) | 77.6 (25.3) | 69.4 (20.8) | 60.1 (15.6) | 53.8 (12.1) | 67.2 (19.6) |
| Average low °F (°C) | 43.6 (6.4) | 46.1 (7.8) | 52.0 (11.1) | 59.7 (15.4) | 68.0 (20.0) | 74.2 (23.4) | 77.1 (25.1) | 76.5 (24.7) | 72.5 (22.5) | 63.2 (17.3) | 53.1 (11.7) | 46.8 (8.2) | 61.1 (16.2) |
| Average precipitation inches (mm) | 2.56 (65) | 2.56 (65) | 3.03 (77) | 2.96 (75) | 2.58 (66) | 4.85 (123) | 5.08 (129) | 6.11 (155) | 5.25 (133) | 4.07 (103) | 2.30 (58) | 2.91 (74) | 44.26 (1,124) |
| Source: NOAA | |||||||||||||
| Climate data for Miami, Florida (1991−2020) | |||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Month | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | Year |
| Average high °F (°C) | 76.2 (24.6) | 78.2 (25.7) | 80.6 (27.0) | 83.6 (28.7) | 86.7 (30.4) | 89.3 (31.8) | 90.6 (32.6) | 90.7 (32.6) | 89.0 (31.7) | 85.9 (29.9) | 81.3 (27.4) | 78.2 (25.7) | 84.2 (29.0) |
| Daily mean °F (°C) | 68.6 (20.3) | 70.7 (21.5) | 73.1 (22.8) | 76.7 (24.8) | 80.1 (26.7) | 82.8 (28.2) | 84.1 (28.9) | 84.2 (29.0) | 83.0 (28.3) | 80.1 (26.7) | 74.8 (23.8) | 71.2 (21.8) | 77.4 (25.2) |
| Average low °F (°C) | 61.0 (16.1) | 63.2 (17.3) | 65.6 (18.7) | 69.8 (21.0) | 73.4 (23.0) | 76.3 (24.6) | 77.5 (25.3) | 77.7 (25.4) | 76.9 (24.9) | 74.2 (23.4) | 68.3 (20.2) | 64.3 (17.9) | 70.7 (21.5) |
| Average precipitation inches (mm) | 1.83 (46) | 2.15 (55) | 2.46 (62) | 3.36 (85) | 6.32 (161) | 10.51 (267) | 7.36 (187) | 9.58 (243) | 10.22 (260) | 7.65 (194) | 3.53 (90) | 2.44 (62) | 67.41 (1,712) |
| Source: NOAA | |||||||||||||
The Northern Interior (the Midwest)
This region includes the states between the western Appalachians and the foothills of the Rocky Mountains approximately to the north of 37°N: western Pennsylvania, North Dakota, South Dakota, Minnesota, Wisconsin, Michigan, Nebraska, Iowa, Illinois, Ohio, Kansas, Missouri, Indiana, Kentucky.
In the valleys of the Ohio, Missouri and northern Mississippi rivers there are extensive plains. Most of the region is below 2,000 feet (600 m) and much of it below 1,000 feet (300 m). It has the most continental climate of any part of the United States. Winters are cold, summers are warm with fairly frequent heat waves and droughts. There is a gradual increase in summer warmth southward and a noticeable increase in the severity and length of winter northward. Winter precipitation is low, especially in the west of this region, and much of it falls as snow. In the north, along the Canadian border and around the Great Lakes, winter conditions can occasionally be severe, with snowstorms as very cold air blows south from the Canadian Arctic.
As you head west, annual rainfall gradually decreases, and droughts are common on the western plains. The eastern states of Michigan, Indiana, Illinois, and Kentucky have much wetter winters than those further west. An unpleasant feature of the weather in the north of this region is the frequent occurrence of freezing rain in winter, when rain falls on the frozen ground from a warm air mass. This can happen five to ten days a year.
Almost the entire region has at least one winter month with an average temperature below freezing, but as the weather is often changeable, even in the middle of winter there can be unusually mild conditions for a few days. Clear skies and lots of sunshine characterize the weather most of the time, even in winter. Sunshine hours per day average between four and five in winter and up to ten or eleven in summer.
A feature of the western part of this region at the foot of the Rocky Mountains is the occasional warm, dry wind, the chinook, which raises the temperature and quickly melts snow in winter and spring. This is a "Föhn" wind that is heated as the air travels down the east side of the mountains.
Characteristic weather for this region is represented by the climate of Omaha, Columbus, and Minneapolis.
| Climate data for Minneapolis, Minnesota (1991–2020) | |||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Month | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | Year |
| Average high °F (°C) | 23.6 (−4.7) | 28.5 (−1.9) | 41.7 (5.4) | 56.6 (13.7) | 69.2 (20.7) | 79.0 (26.1) | 83.4 (28.6) | 80.7 (27.1) | 72.9 (22.7) | 58.1 (14.5) | 41.9 (5.5) | 28.8 (−1.8) | 55.4 (13.0) |
| Daily mean °F (°C) | 16.2 (−8.8) | 20.6 (−6.3) | 33.3 (0.7) | 47.1 (8.4) | 59.5 (15.3) | 69.7 (20.9) | 74.3 (23.5) | 71.8 (22.1) | 63.5 (17.5) | 49.5 (9.7) | 34.8 (1.6) | 22.0 (−5.6) | 46.9 (8.3) |
| Average low °F (°C) | 8.8 (−12.9) | 12.7 (−10.7) | 24.9 (−3.9) | 37.5 (3.1) | 49.9 (9.9) | 60.4 (15.8) | 65.3 (18.5) | 62.8 (17.1) | 54.2 (12.3) | 40.9 (4.9) | 27.7 (−2.4) | 15.2 (−9.3) | 38.4 (3.6) |
| Average precipitation inches (mm) | 0.89 (23) | 0.87 (22) | 1.68 (43) | 2.91 (74) | 3.91 (99) | 4.58 (116) | 4.06 (103) | 4.34 (110) | 3.02 (77) | 2.58 (66) | 1.61 (41) | 1.17 (30) | 31.62 (803) |
| Average snowfall inches (cm) | 11.0 (28) | 9.5 (24) | 8.2 (21) | 3.5 (8.9) | 0.0 (0.0) | 0.0 (0.0) | 0.0 (0.0) | 0.0 (0.0) | 0.0 (0.0) | 0.8 (2.0) | 6.8 (17) | 11.4 (29) | 51.2 (130) |
| Source: NOAA | |||||||||||||
| Climate data for Columbus, Ohio (1991–2020) | |||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Month | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | Year |
| Average high °F (°C) | 37.1 (2.8) | 40.8 (4.9) | 51.1 (10.6) | 64.1 (17.8) | 74.1 (23.4) | 82.2 (27.9) | 85.4 (29.7) | 84.1 (28.9) | 77.8 (25.4) | 65.5 (18.6) | 52.3 (11.3) | 41.5 (5.3) | 63.0 (17.2) |
| Daily mean °F (°C) | 29.6 (−1.3) | 32.5 (0.3) | 41.6 (5.3) | 53.2 (11.8) | 63.3 (17.4) | 71.9 (22.2) | 75.4 (24.1) | 74.0 (23.3) | 67.2 (19.6) | 55.2 (12.9) | 43.6 (6.4) | 34.5 (1.4) | 53.5 (11.9) |
| Average low °F (°C) | 22.0 (−5.6) | 24.2 (−4.3) | 32.0 (0.0) | 42.2 (5.7) | 52.4 (11.3) | 61.6 (16.4) | 65.4 (18.6) | 63.9 (17.7) | 56.5 (13.6) | 44.8 (7.1) | 35.0 (1.7) | 27.4 (−2.6) | 43.9 (6.6) |
| Average precipitation inches (mm) | 3.00 (76) | 2.41 (61) | 3.62 (92) | 3.85 (98) | 3.99 (101) | 4.33 (110) | 4.67 (119) | 3.74 (95) | 3.14 (80) | 2.90 (74) | 2.79 (71) | 3.13 (80) | 41.57 (1,056) |
| Average snowfall inches (cm) | 9.5 (24) | 7.6 (19) | 4.1 (10) | 0.5 (1.3) | 0.0 (0.0) | 0.0 (0.0) | 0.0 (0.0) | 0.0 (0.0) | 0.0 (0.0) | 0.2 (0.51) | 1.2 (3.0) | 5.1 (13) | 28.2 (72) |
| Source: NOAA | |||||||||||||
| Climate data for Omaha, Nebraska (1991–2020) | |||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Month | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | Year |
| Average high °F (°C) | 33.6 (0.9) | 38.6 (3.7) | 52.1 (11.2) | 64.1 (17.8) | 74.6 (23.7) | 84.4 (29.1) | 88.1 (31.2) | 85.8 (29.9) | 79.1 (26.2) | 65.5 (18.6) | 50.3 (10.2) | 37.7 (3.2) | 62.8 (17.1) |
| Daily mean °F (°C) | 24.4 (−4.2) | 28.9 (−1.7) | 41.0 (5.0) | 52.6 (11.4) | 63.6 (17.6) | 73.9 (23.3) | 78.1 (25.6) | 75.7 (24.3) | 67.6 (19.8) | 54.4 (12.4) | 40.2 (4.6) | 28.7 (−1.8) | 52.4 (11.3) |
| Average low °F (°C) | 15.2 (−9.3) | 19.3 (−7.1) | 30.0 (−1.1) | 41.1 (5.1) | 52.7 (11.5) | 63.4 (17.4) | 68.0 (20.0) | 65.6 (18.7) | 56.1 (13.4) | 43.2 (6.2) | 30.2 (−1.0) | 19.8 (−6.8) | 42.1 (5.6) |
| Average precipitation inches (mm) | 0.75 (19) | 0.95 (24) | 1.79 (45) | 3.17 (81) | 4.66 (118) | 4.44 (113) | 3.55 (90) | 4.60 (117) | 2.96 (75) | 2.32 (59) | 1.45 (37) | 1.22 (31) | 31.86 (809) |
| Average snowfall inches (cm) | 7.2 (18) | 7.8 (20) | 3.0 (7.6) | 1.0 (2.5) | 0.1 (0.25) | 0.0 (0.0) | 0.0 (0.0) | 0.0 (0.0) | 0.0 (0.0) | 0.5 (1.3) | 1.7 (4.3) | 5.8 (15) | 27.1 (69) |
| Source: NOAA | |||||||||||||
The Southern Interior and Gulf States
Including Oklahoma, Arkansas, Tennessee, Texas, Louisiana, Mississippi, Alabama.
This large region includes the states approximately south of 37°N between the Rocky Mountains and the Appalachian Mountains and those bordering the Gulf of Mexico. The weather pattern throughout the year is quite similar to that of the Midwest; However, because it's further south and more exposed to warm tropical air from the Atlantic Ocean and Gulf of Mexico, winters are both warmer and shorter than further north. It is rare for a winter month to have an average temperature below freezing here, but occasional very cold spells can last for a few days as arctic air enters this region from the north. Occasionally even snow and frost can hit the shores of the Gulf of Mexico, and in west Texas such cold spells are more frequent and severe. Summers are slightly warmer than further north, but the increasing length of the summer period and the warmth of spring and autumn are more evident.
The eastern part of this region is much wetter than the west. Annual rainfall ranges from 1,000 to 1,250 millimeters (40 to 50 inches) almost everywhere in the east, but only 350 to 500 millimeters (15 to 20 inches) in the west. Summer is the wettest season and thunderstorms are very common in the east of this region. Parts of the states of Tennessee and Alabama include the southern Appalachians; here the winter precipitation is heavier and the weather and climate are more similar to those of the East Atlantic states.
Most of the region has a sunny climate, particularly western parts of Texas and Oklahoma. Sunshine hours per day range from five or six in winter to ten or eleven in summer. The summer heat is rarely uncomfortable except along the Gulf of Mexico coast where the combination of heat and humidity can be oppressive. This region is hit by hurricanes and tornadoes.
Weather characteristic of this region is shown by the climate for Little Rock, Houston, and Jackson.
| Climate data for Little Rock, Arkansas (1991−2020) | |||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Month | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | Year |
| Average high °F (°C) | 50.5 (10.3) | 55.2 (12.9) | 63.7 (17.6) | 72.8 (22.7) | 80.5 (26.9) | 88.2 (31.2) | 91.7 (33.2) | 91.5 (33.1) | 85.1 (29.5) | 74.2 (23.4) | 61.9 (16.6) | 52.6 (11.4) | 72.3 (22.4) |
| Daily mean °F (°C) | 40.7 (4.8) | 44.7 (7.1) | 52.7 (11.5) | 61.4 (16.3) | 69.9 (21.1) | 78.0 (25.6) | 81.4 (27.4) | 80.8 (27.1) | 74.0 (23.3) | 62.6 (17.0) | 51.1 (10.6) | 43.0 (6.1) | 61.7 (16.5) |
| Average low °F (°C) | 30.9 (−0.6) | 34.2 (1.2) | 41.8 (5.4) | 50.1 (10.1) | 59.3 (15.2) | 67.7 (19.8) | 71.2 (21.8) | 70.1 (21.2) | 62.9 (17.2) | 50.9 (10.5) | 40.2 (4.6) | 33.3 (0.7) | 51.0 (10.6) |
| Average precipitation inches (mm) | 3.50 (89) | 3.97 (101) | 4.96 (126) | 5.59 (142) | 5.08 (129) | 3.55 (90) | 3.33 (85) | 3.16 (80) | 3.01 (76) | 4.47 (114) | 4.72 (120) | 5.08 (129) | 50.42 (1,281) |
| Source: NOAA | |||||||||||||
| Climate data for Jackson, Mississippi (1991–2020) | |||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Month | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | Year |
| Average high °F (°C) | 57.4 (14.1) | 62.0 (16.7) | 69.4 (20.8) | 76.5 (24.7) | 83.8 (28.8) | 89.9 (32.2) | 92.1 (33.4) | 92.2 (33.4) | 87.8 (31.0) | 78.3 (25.7) | 67.2 (19.6) | 59.6 (15.3) | 76.4 (24.7) |
| Daily mean °F (°C) | 47.0 (8.3) | 50.9 (10.5) | 57.9 (14.4) | 64.9 (18.3) | 72.9 (22.7) | 79.6 (26.4) | 82.1 (27.8) | 81.8 (27.7) | 76.9 (24.9) | 66.2 (19.0) | 55.4 (13.0) | 49.1 (9.5) | 65.4 (18.6) |
| Average low °F (°C) | 36.6 (2.6) | 39.8 (4.3) | 46.4 (8.0) | 53.3 (11.8) | 62.1 (16.7) | 69.4 (20.8) | 72.2 (22.3) | 71.5 (21.9) | 66.0 (18.9) | 54.2 (12.3) | 43.6 (6.4) | 38.7 (3.7) | 54.5 (12.5) |
| Average precipitation inches (mm) | 5.42 (138) | 5.10 (130) | 5.68 (144) | 5.84 (148) | 4.36 (111) | 4.43 (113) | 5.02 (128) | 4.69 (119) | 3.48 (88) | 3.80 (97) | 4.40 (112) | 5.13 (130) | 57.35 (1,457) |
| Source: NOAA | |||||||||||||
| Climate data for Houston, Texas (1991–2020) | |||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Month | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | Year |
| Average high °F (°C) | 63.8 (17.7) | 67.6 (19.8) | 73.4 (23.0) | 79.3 (26.3) | 85.9 (29.9) | 91.0 (32.8) | 92.9 (33.8) | 93.5 (34.2) | 89.3 (31.8) | 82.1 (27.8) | 72.6 (22.6) | 65.7 (18.7) | 79.8 (26.6) |
| Daily mean °F (°C) | 55.0 (12.8) | 58.9 (14.9) | 64.7 (18.2) | 70.6 (21.4) | 77.6 (25.3) | 83.0 (28.3) | 84.8 (29.3) | 85.1 (29.5) | 81.1 (27.3) | 73.0 (22.8) | 63.3 (17.4) | 56.9 (13.8) | 71.2 (21.8) |
| Average low °F (°C) | 46.1 (7.8) | 50.1 (10.1) | 55.9 (13.3) | 61.8 (16.6) | 69.3 (20.7) | 74.9 (23.8) | 76.6 (24.8) | 76.7 (24.8) | 72.9 (22.7) | 63.9 (17.7) | 54.0 (12.2) | 48.0 (8.9) | 62.5 (16.9) |
| Average precipitation inches (mm) | 4.09 (104) | 2.85 (72) | 3.28 (83) | 4.08 (104) | 5.42 (138) | 6.09 (155) | 4.59 (117) | 5.44 (138) | 5.76 (146) | 5.78 (147) | 3.90 (99) | 4.34 (110) | 55.62 (1,413) |
| Source: NOAA | |||||||||||||
The States of the Rocky Mountains Region
Including the mountainous country comprising all or large parts of Montana, Idaho, Wyoming, Nevada, Utah, Colorado, Arizona, New Mexico, western Texas.
This region can be divided between the three northern states of Idaho, Montana, Wyoming and the remaining Rocky Mountain states. In general, these northern states are cooler in both winter and summer, have a much longer cold season, and are generally wetter than those further south. However, within this entire region there is so much local variation in temperature and rainfall due to the differences in altitude that one can find cold spots in the south of the region and some dry areas in the north. Altitude has a big impact on temperature—for example, there isn't much of a difference between precipitation and temperature for Cheyenne in Wyoming and Santa Fé in New Mexico, both of which are higher 6,000 feet (1,800 m). On the other hand, temperatures in Phoenix, Arizona at 1,000 feet (330 m) are much higher than in Santa Fe for all months.
Much of this region has little rainfall, particularly in the south where large areas of Arizona, New Mexico, Utah, and Colorado are desert or semi-desert with annual rainfall of less than 300 millimeters (12 inches) or even 200 millimeters (8 inches). This is because the rain shadow of the western mountains of California removes much of the moisture from the incoming air from the Pacific. It is also a result of the frequent and prolonged anticyclonic weather that is prevalent in this region.
Some extremely low temperatures have been recorded at various locations in the north of this mountainous region; and some very high temperatures have occurred in the south. The southern portion has the sunniest climate in the United States; Both Phoenix and Las Vegas get about eight hours of sunshine per day in the winter and between twelve and thirteen hours in the summer months. The high summer temperatures in this area are made more bearable by the low humidity.
| Climate data for Cheyenne, Wyoming (1991–2020) | |||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Month | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | Year |
| Average high °F (°C) | 40.0 (4.4) | 40.6 (4.8) | 49.1 (9.5) | 54.8 (12.7) | 64.4 (18.0) | 76.7 (24.8) | 84.1 (28.9) | 82.0 (27.8) | 73.3 (22.9) | 59.1 (15.1) | 47.5 (8.6) | 39.3 (4.1) | 59.2 (15.1) |
| Daily mean °F (°C) | 29.2 (−1.6) | 29.5 (−1.4) | 37.1 (2.8) | 42.8 (6.0) | 52.3 (11.3) | 63.1 (17.3) | 70.1 (21.2) | 68.1 (20.1) | 59.6 (15.3) | 46.5 (8.1) | 36.1 (2.3) | 28.7 (−1.8) | 46.9 (8.3) |
| Average low °F (°C) | 18.4 (−7.6) | 18.4 (−7.6) | 25.1 (−3.8) | 30.8 (−0.7) | 40.2 (4.6) | 49.4 (9.7) | 56.1 (13.4) | 54.3 (12.4) | 45.8 (7.7) | 33.9 (1.1) | 24.7 (−4.1) | 18.1 (−7.7) | 34.6 (1.4) |
| Average precipitation inches (mm) | 0.35 (8.9) | 0.52 (13) | 0.96 (24) | 1.79 (45) | 2.44 (62) | 2.16 (55) | 2.11 (54) | 1.52 (39) | 1.47 (37) | 1.00 (25) | 0.61 (15) | 0.48 (12) | 15.41 (391) |
| Average snowfall inches (cm) | 6.3 (16) | 9.0 (23) | 9.7 (25) | 11.3 (29) | 3.4 (8.6) | 0.0 (0.0) | 0.0 (0.0) | 0.0 (0.0) | 1.0 (2.5) | 5.9 (15) | 7.5 (19) | 8.8 (22) | 62.9 (160) |
| Source: NOAA | |||||||||||||
| Climate data for Santa Fe, New Mexico (1981–2010) | |||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Month | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | Year |
| Average high °F (°C) | 43.5 (6.4) | 48.2 (9.0) | 55.9 (13.3) | 64.7 (18.2) | 74.2 (23.4) | 83.5 (28.6) | 85.9 (29.9) | 83.4 (28.6) | 77.7 (25.4) | 66.5 (19.2) | 53.1 (11.7) | 43.2 (6.2) | 65.0 (18.3) |
| Daily mean °F (°C) | 30.5 (−0.8) | 34.9 (1.6) | 41.0 (5.0) | 48.5 (9.2) | 57.6 (14.2) | 66.5 (19.2) | 70.1 (21.2) | 68.4 (20.2) | 62.1 (16.7) | 51.0 (10.6) | 38.9 (3.8) | 30.3 (−0.9) | 50.0 (10.0) |
| Average low °F (°C) | 17.5 (−8.1) | 21.5 (−5.8) | 26.1 (−3.3) | 32.3 (0.2) | 41.0 (5.0) | 49.4 (9.7) | 54.4 (12.4) | 53.3 (11.8) | 46.5 (8.1) | 35.5 (1.9) | 24.6 (−4.1) | 17.4 (−8.1) | 35.0 (1.7) |
| Average precipitation inches (mm) | 0.60 (15) | 0.53 (13) | 0.94 (24) | 0.77 (20) | 0.94 (24) | 1.29 (33) | 2.33 (59) | 2.23 (57) | 1.54 (39) | 1.33 (34) | 0.85 (22) | 0.83 (21) | 14.18 (360) |
| Average snowfall inches (cm) | 4.0 (10) | 2.9 (7.4) | 4.4 (11) | 0.4 (1.0) | 0 (0) | 0 (0) | 0 (0) | 0 (0) | 0 (0) | 1.0 (2.5) | 2.3 (5.8) | 8.0 (20) | 23 (58) |
| Source: NOAA | |||||||||||||
| Climate data for Phoenix, Arizona (1991–2020) | |||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Month | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | Year |
| Average high °F (°C) | 67.6 (19.8) | 70.8 (21.6) | 78.1 (25.6) | 85.5 (29.7) | 94.5 (34.7) | 104.2 (40.1) | 106.5 (41.4) | 105.1 (40.6) | 100.4 (38.0) | 89.2 (31.8) | 76.5 (24.7) | 66.2 (19.0) | 87.1 (30.6) |
| Daily mean °F (°C) | 56.8 (13.8) | 59.9 (15.5) | 66.3 (19.1) | 73.2 (22.9) | 82.0 (27.8) | 91.4 (33.0) | 95.5 (35.3) | 94.4 (34.7) | 89.2 (31.8) | 77.4 (25.2) | 65.1 (18.4) | 55.8 (13.2) | 75.6 (24.2) |
| Average low °F (°C) | 46.0 (7.8) | 49.0 (9.4) | 54.5 (12.5) | 60.8 (16.0) | 69.5 (20.8) | 78.6 (25.9) | 84.5 (29.2) | 83.6 (28.7) | 78.1 (25.6) | 65.6 (18.7) | 53.7 (12.1) | 45.3 (7.4) | 64.1 (17.8) |
| Average precipitation inches (mm) | 0.87 (22) | 0.87 (22) | 0.83 (21) | 0.22 (5.6) | 0.13 (3.3) | 0.02 (0.51) | 0.91 (23) | 0.93 (24) | 0.57 (14) | 0.56 (14) | 0.57 (14) | 0.74 (19) | 7.22 (183) |
| Source: NOAA | |||||||||||||
The States of the Pacific Northwest
Including Washington, Oregon, western Idaho.
The North West region has a weather and climate very similar to that of North West Europe and the UK in particular. This region includes a range of high mountains that rise to over 14,000 feet (4,250 m) and are snow-capped all year round. Therefore, the higher parts of these two states bear some resemblance to the weather and climate of the northern part of the Rocky Mountains.
The coastal areas have the lowest annual temperature variation in the United States; winters are mild and summers are only moderately warm. It is a cloudy region and the least sunny part of the US with a large number of rainy days. Some of the mountain areas are very wet with up to 2,500 to 3,000 millimeters (100 to 120 inches) of rainfall per year. In the sheltered valleys and in some of the extensive high plateau districts, on the other hand, only 300 mm (12 inches) of annual precipitation falls. This is also the only region of the country where winter is the wettest season, although all months can experience rain and changeable weather. There are few summer droughts like those further south in California.
Summer sea fog can affect some of the coastal areas, reducing solar radiation and lowering temperatures. The region owes its wetness and mildness to the influence of the Pacific Ocean and the frequent passage of cyclonic lows that originate on the North Pacific polar front. The air masses do not have the temperature extremes that give so many parts of the interior of the United States frequent alternations of warm and very cold weather, and a great contrast between summer heat and winter chill.
The average number of hours of sunshine per day on the coast ranges from two to three in winter and nine to ten in summer. Inland and at higher elevations, winters are sunnier, with five to six hours a day.
The climate of Seattle and Eugene are representative of the coastal districts, while that for Boise are typical of areas farther inland at moderate altitude.
| Climate data for Seattle, Washington (1991–2020) | |||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Month | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | Year |
| Average high °F (°C) | 48.0 (8.9) | 50.3 (10.2) | 54.2 (12.3) | 59.3 (15.2) | 66.3 (19.1) | 71.1 (21.7) | 77.4 (25.2) | 77.6 (25.3) | 71.6 (22.0) | 60.5 (15.8) | 52.1 (11.2) | 47.0 (8.3) | 61.3 (16.3) |
| Daily mean °F (°C) | 42.8 (6.0) | 44.0 (6.7) | 47.1 (8.4) | 51.3 (10.7) | 57.5 (14.2) | 62.0 (16.7) | 67.1 (19.5) | 67.4 (19.7) | 62.6 (17.0) | 53.8 (12.1) | 46.5 (8.1) | 42.0 (5.6) | 53.7 (12.1) |
| Average low °F (°C) | 37.7 (3.2) | 37.7 (3.2) | 39.9 (4.4) | 43.3 (6.3) | 48.7 (9.3) | 53.0 (11.7) | 56.8 (13.8) | 57.2 (14.0) | 53.6 (12.0) | 47.0 (8.3) | 40.9 (4.9) | 37.1 (2.8) | 46.1 (7.8) |
| Average precipitation inches (mm) | 5.78 (147) | 3.76 (96) | 4.17 (106) | 3.18 (81) | 1.88 (48) | 1.45 (37) | 0.60 (15) | 0.97 (25) | 1.61 (41) | 3.91 (99) | 6.31 (160) | 5.72 (145) | 39.34 (999) |
| Average snowfall inches (cm) | 1.8 (4.6) | 2.2 (5.6) | 0.4 (1.0) | 0.0 (0.0) | 0.0 (0.0) | 0.0 (0.0) | 0.0 (0.0) | 0.0 (0.0) | 0.0 (0.0) | 0.0 (0.0) | 0.2 (0.51) | 1.7 (4.3) | 6.3 (16) |
| Source: NOAA | |||||||||||||
| Climate data for Eugene, Oregon (1981–2010) | |||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Month | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | Year |
| Average high °F (°C) | 47.2 (8.4) | 51.1 (10.6) | 56.2 (13.4) | 60.8 (16.0) | 67.0 (19.4) | 73.2 (22.9) | 82.3 (27.9) | 82.8 (28.2) | 76.9 (24.9) | 64.2 (17.9) | 52.2 (11.2) | 45.6 (7.6) | 63.4 (17.4) |
| Daily mean °F (°C) | 40.7 (4.8) | 42.9 (6.1) | 46.7 (8.2) | 50.2 (10.1) | 55.3 (12.9) | 60.4 (15.8) | 66.8 (19.3) | 66.9 (19.4) | 61.9 (16.6) | 52.7 (11.5) | 44.9 (7.2) | 39.7 (4.3) | 52.4 (11.4) |
| Average low °F (°C) | 34.2 (1.2) | 34.8 (1.6) | 37.1 (2.8) | 39.5 (4.2) | 43.5 (6.4) | 47.6 (8.7) | 51.4 (10.8) | 51.1 (10.6) | 47.0 (8.3) | 41.2 (5.1) | 37.6 (3.1) | 33.8 (1.0) | 41.6 (5.3) |
| Average precipitation inches (mm) | 6.87 (174) | 5.43 (138) | 4.99 (127) | 3.33 (85) | 2.74 (70) | 1.50 (38) | 0.54 (14) | 0.61 (15) | 1.29 (33) | 3.25 (83) | 7.72 (196) | 7.83 (199) | 46.10 (1,171) |
| Average snowfall inches (cm) | 0.8 (2.0) | 2.4 (6.1) | trace | 0 (0) | 0 (0) | 0 (0) | 0 (0) | 0 (0) | 0 (0) | 0 (0) | 0.2 (0.51) | 1.5 (3.8) | 4.9 (12) |
| Source: NOAA | |||||||||||||
| Climate data for Boise, Idaho (1991–2020) | |||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Month | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | Year |
| Average high °F (°C) | 38.8 (3.8) | 46.0 (7.8) | 55.5 (13.1) | 62.3 (16.8) | 72.3 (22.4) | 81.4 (27.4) | 92.7 (33.7) | 90.7 (32.6) | 80.0 (26.7) | 64.8 (18.2) | 48.8 (9.3) | 38.8 (3.8) | 64.3 (17.9) |
| Daily mean °F (°C) | 32.2 (0.1) | 37.5 (3.1) | 45.2 (7.3) | 50.9 (10.5) | 59.9 (15.5) | 67.8 (19.9) | 77.3 (25.2) | 75.8 (24.3) | 66.3 (19.1) | 53.2 (11.8) | 40.3 (4.6) | 32.1 (0.1) | 53.2 (11.8) |
| Average low °F (°C) | 25.5 (−3.6) | 29.0 (−1.7) | 34.9 (1.6) | 39.6 (4.2) | 47.5 (8.6) | 54.1 (12.3) | 61.9 (16.6) | 60.8 (16.0) | 52.6 (11.4) | 41.5 (5.3) | 31.7 (−0.2) | 25.4 (−3.7) | 42.0 (5.6) |
| Average precipitation inches (mm) | 1.41 (36) | 1.00 (25) | 1.33 (34) | 1.23 (31) | 1.45 (37) | 0.75 (19) | 0.21 (5.3) | 0.17 (4.3) | 0.43 (11) | 0.81 (21) | 1.18 (30) | 1.54 (39) | 11.51 (292) |
| Average snowfall inches (cm) | 5.3 (13) | 3.3 (8.4) | 1.2 (3.0) | 0.1 (0.25) | 0.0 (0.0) | 0.0 (0.0) | 0.0 (0.0) | 0.0 (0.0) | 0.0 (0.0) | 0.1 (0.25) | 2.0 (5.1) | 5.6 (14) | 17.6 (45) |
| Source: NOAA | |||||||||||||
California
California has a very distinct Mediterranean climate. The north coast of California has a similar climate to the coastal areas of the Northwest, but there is a gradual increase in summer temperature southward and a decrease in rainfall until summers in central and southern California become completely dry. In the state's southeast, rainfall decreases until conditions resemble those of the desert regions of neighboring Arizona and northern Mexico. Most of California enjoys mild and moderately wet winters and warm to hot and very dry summers. There are some major mountain regions within the state: the coastal areas and the Sierra Nevada, which rise to over 12,000 feet (3,700 m). These mountains have heavy rainfall and much of it snow at higher elevations, allowing for plenty of winter sports activities in a state often associated with sun, sea and warmth.
The climate of San Francisco and Los Angeles is representative of the coastal region. San Francisco has unusually cool to mild summers. This is a very local feature, caused by the frequent sea fog that sweeps into the bay through the Golden Gate gap in the coast chain. Elsewhere, this sea fog rarely affects land, but the cool waters of the California Current help summer temperatures to be much lower on the coast than inland. In the Great Valley of California and the desert areas of the Southeast, summer temperatures are much higher. Frost and snow are very rare on the coast but are more common inland in winter. The climate of Death Valley shows the extremely high temperatures here in summer. This location has not only experienced the highest temperatures in the United States, but also some of the highest on record anywhere in the world.
California's winter precipitation, however, is caused by the same sequence of cyclonic lows that bring rain to the northwest states. In summer, such disturbances are pushed further north by the presence of the North Pacific subtropical anticyclone, which brings calm, calm, and sunny weather for most of the season.
California therefore has a very pleasant climate all year round: sunny and dry with only short periods of relatively cold weather in winter, although very heavy snowstorms occur in the mountains. California is one of the sunniest states in the country. Sunshine hours per day average from seven to eight in winter to twelve to fourteen in summer in the driest inland regions. On the coast it is rather less: from six to seven in winter and from nine to ten in summer. The decline of the summer sun on the coast is due to sea fog.
| Climate data for San Francisco (1991–2020) | |||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Month | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | Year |
| Average high °F (°C) | 57.8 (14.3) | 60.4 (15.8) | 62.1 (16.7) | 63.0 (17.2) | 64.1 (17.8) | 66.5 (19.2) | 66.3 (19.1) | 67.9 (19.9) | 70.2 (21.2) | 69.8 (21.0) | 63.7 (17.6) | 57.9 (14.4) | 64.1 (17.8) |
| Daily mean °F (°C) | 52.2 (11.2) | 54.2 (12.3) | 55.5 (13.1) | 56.4 (13.6) | 57.8 (14.3) | 59.7 (15.4) | 60.3 (15.7) | 61.7 (16.5) | 62.9 (17.2) | 62.1 (16.7) | 57.2 (14.0) | 52.5 (11.4) | 57.7 (14.3) |
| Average low °F (°C) | 46.6 (8.1) | 47.9 (8.8) | 48.9 (9.4) | 49.7 (9.8) | 51.4 (10.8) | 53.0 (11.7) | 54.4 (12.4) | 55.5 (13.1) | 55.6 (13.1) | 54.4 (12.4) | 50.7 (10.4) | 47.0 (8.3) | 51.3 (10.7) |
| Average precipitation inches (mm) | 4.40 (112) | 4.37 (111) | 3.15 (80) | 1.60 (41) | 0.70 (18) | 0.20 (5.1) | 0.01 (0.25) | 0.06 (1.5) | 0.10 (2.5) | 0.94 (24) | 2.60 (66) | 4.76 (121) | 22.89 (581) |
| Source: NOAA | |||||||||||||
| Climate data for Los Angeles (1991–2020) | |||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Month | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | Year |
| Average high °F (°C) | 68.0 (20.0) | 68.0 (20.0) | 69.9 (21.1) | 72.4 (22.4) | 73.7 (23.2) | 77.2 (25.1) | 82.0 (27.8) | 84.0 (28.9) | 83.0 (28.3) | 78.6 (25.9) | 72.9 (22.7) | 67.4 (19.7) | 74.8 (23.8) |
| Daily mean °F (°C) | 58.4 (14.7) | 59.0 (15.0) | 61.1 (16.2) | 63.6 (17.6) | 65.9 (18.8) | 69.3 (20.7) | 73.3 (22.9) | 74.7 (23.7) | 73.6 (23.1) | 69.3 (20.7) | 63.0 (17.2) | 57.8 (14.3) | 65.8 (18.8) |
| Average low °F (°C) | 48.9 (9.4) | 50.0 (10.0) | 52.4 (11.3) | 54.8 (12.7) | 58.1 (14.5) | 61.4 (16.3) | 64.7 (18.2) | 65.4 (18.6) | 64.2 (17.9) | 59.9 (15.5) | 53.1 (11.7) | 48.2 (9.0) | 56.8 (13.8) |
| Average precipitation inches (mm) | 3.29 (84) | 3.64 (92) | 2.23 (57) | 0.69 (18) | 0.32 (8.1) | 0.09 (2.3) | 0.02 (0.51) | 0.00 (0.00) | 0.13 (3.3) | 0.58 (15) | 0.78 (20) | 2.48 (63) | 14.25 (362) |
| Source: NOAA | |||||||||||||
| Climate data for Death Valley National Park (1991–2020) | |||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Month | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | Year |
| Average high °F (°C) | 67.2 (19.6) | 73.7 (23.2) | 82.6 (28.1) | 91.0 (32.8) | 100.7 (38.2) | 111.1 (43.9) | 117.4 (47.4) | 115.9 (46.6) | 107.7 (42.1) | 93.3 (34.1) | 77.4 (25.2) | 65.6 (18.7) | 92.0 (33.3) |
| Daily mean °F (°C) | 54.9 (12.7) | 61.3 (16.3) | 69.8 (21.0) | 77.9 (25.5) | 87.8 (31.0) | 97.5 (36.4) | 104.2 (40.1) | 102.3 (39.1) | 93.4 (34.1) | 78.9 (26.1) | 64.0 (17.8) | 53.4 (11.9) | 78.8 (26.0) |
| Average low °F (°C) | 42.5 (5.8) | 49.0 (9.4) | 57.1 (13.9) | 64.8 (18.2) | 75.0 (23.9) | 84.0 (28.9) | 91.0 (32.8) | 88.7 (31.5) | 79.1 (26.2) | 64.4 (18.0) | 50.5 (10.3) | 41.1 (5.1) | 65.6 (18.7) |
| Average precipitation inches (mm) | 0.37 (9.4) | 0.52 (13) | 0.25 (6.4) | 0.10 (2.5) | 0.03 (0.76) | 0.05 (1.3) | 0.10 (2.5) | 0.10 (2.5) | 0.20 (5.1) | 0.12 (3.0) | 0.10 (2.5) | 0.26 (6.6) | 2.20 (56) |
| Source: NOAA | |||||||||||||
References
- E. A. Pearce, Charles Gordon Smith, (1990) The Hutchinson World Weather Guide, John Murray Press. ISBN 1859863426
- Timothy L. Gall, (ed.), (2003), Worldmark Encyclopedia of the Nations, Eleventh Edition, Thomson Gale
- Hugh Chisholm, (ed.), (1911), Encyclopædia Britannica, Eleventh edition, Cambridge University Press
The Climate of
the United States
In summary:
The greater part of the continental United States has a temperate or continental climate. The average annual temperatures vary from somewhat less than 50°F (10°C) on the northern border to 75°F (24°C) in the extreme southeast. The average maximum temperatures is as high as 115° to 120°F (46 to 49°C) in the drier portions of Texas and Arizona, and the average minimum falls as low as -40°F (-40°C) in northern Minnesota. There is a great contrast between the Atlantic and Pacific coasts. In general the Pacific coast is under the influence of south and west winds, which bring abundant winter rains to northern California, Oregon, and Washington without severe cold weather. On the Atlantic coast the winter rains and snows are followed by very cold weather.
The heaviest rain occurs on the coast of Oregon and Washington; next to this are the humidity and rainfall of the coasts of Florida and the adjacent States. Throughout the Mississippi Valley and along the Atlantic coast there are great fluctuations in rainfall. The driest portion of the continent extends from southern California and Arizona eastward over the eastern slopes of the Rocky Mountain region.