The Climate of the
Northern Mariana Islands
Street in Garapan
What is the climate of the Northern Mariana Islands like?
The Northern Mariana Islands is a self-governing commonwealth of the United States in the Western Pacific Ocean. It occupies the islands in the Mariana group, excluding Guam (a separate political entity). Located between 12° and 21°N, it consists of 16 volcanic islands. Only six of the islands are inhabited, and most of the people live on the three largest islands—Rota, Saipan, and Tinian. The country experiences much the same weather as the other island groups in the western Pacific north of the equator—Micronesia, and the Marshall Islands. Rainfall is significantly less, though, in the northernmost islands.
Conditions of temperature and humidity vary little throughout the year. The country has a typical tropical oceanic climate, with moderately high temperatures and humidity. The daily range of temperature is quite small—about 4°–5° C/10°F. Temperatures average 21–29°C (70–85°F), and relative humidity is generally high. Rainfall averages 2,100 millimeters (85 inches) per year. There is abundant to moderately heavy rainfall with a wetter season from June to November. The actual amount of rainfall on each island depends both on the altitude of the land and on exposure to the dominant winds: the northeast trade winds in the low-sun period and the southeast monsoon in the high-sun period.
The country is liable to tropical cyclones with their heavy rainfall and very strong winds, which can do considerable damage. The main season for such storms is from July to November. The worst of them may only affect one particular island every two or three years, but the much larger area of heavy rain associated with a cyclone contributes to the heavier rainfall of these months.
The Northern Marianas have moderately large amounts of sunshine, averaging between six and eight hours a day, in spite of a large number of days on which some rain falls. Much of the rainfall is in the form of short, heavy showers but days with continuous rain are more frequent in the wetter months. Although the combination of temperature and humidity is often rather muggy and oppressive, particularly at night, the daytime temperatures are usually moderate and feel more comfortable because of the brisk winds, both daytime sea breezes and the predominant and regular trade winds.
The climate of Saipan illustrates conditions in the Marianas.
| Climate data for Saipan | |||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Month | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | Year |
| Average high °F (°C) | 81.2 (27.3) | 79.7 (26.5) | 79.8 (26.6) | 83.1 (28.4) | 84.4 (29.1) | 85.0 (29.4) | 84.1 (28.9) | 84.0 (28.9) | 83.8 (28.8) | 83.7 (28.7) | 83.3 (28.5) | 81.4 (27.4) | 82.8 (28.2) |
| Daily mean °F (°C) | 77.3 (25.2) | 76.3 (24.6) | 76.4 (24.7) | 78.5 (25.8) | 79.9 (26.6) | 80.2 (26.8) | 79.6 (26.4) | 79.6 (26.4) | 79.4 (26.3) | 79.3 (26.3) | 79.1 (26.2) | 77.8 (25.4) | 78.6 (25.9) |
| Average low °F (°C) | 73.4 (23.0) | 72.9 (22.7) | 73.1 (22.8) | 73.9 (23.3) | 75.5 (24.2) | 75.3 (24.1) | 75.1 (23.9) | 75.2 (24.0) | 75.0 (23.9) | 74.9 (23.8) | 75.0 (23.9) | 74.1 (23.4) | 74.5 (23.6) |
| Average rainfall inches (mm) | 3.84 (98) | 4.42 (112) | 2.40 (61) | 5.03 (128) | 3.80 (97) | 5.04 (128) | 10.16 (258) | 12.42 (315) | 11.65 (296) | 10.99 (279) | 7.76 (197) | 5.88 (149) | 83.39 (2,118) |
| 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
Northern Mariana Islands
In summary:
The climate of the Northern Mariana Islands is tropical, with relatively little seasonal change; temperatures average 70–85°F (21–29°C), and relative humidity is generally high. Rainfall averages 85 in (2100 mm) per year.