Northern Mariana Islands
This self-governing commonwealth of the United States, occupies the northern islands in the Marianas group, which experience much the same weather as three other island groups in the western Pacific north of the equator - the Caroline, Gilbert, and Marshall Islands. Rainfall is significantly less, though, in the northernmost islands of the country.
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.
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 (the typhoons of the South China Sea) 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 table for Saipan illustrates conditions in the Marianas.
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