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The climate of Guam
Guam is an island situated in Oceania. Guam that counts 549 square kilometers is not an independent country but a separate territory of the United States of America. Guam belongs to the region of Micronesia. The climate of Guam is a tropical rainforest climate, which in the Köppen-Geiger climate classification is indicated with the letter code Af. Guam has a drier and a wet season. This wet season starts in July and lasts up to and including November. In this period the amounts of precipitation can easily rise to three-hundred millimeters per month and in some years even to nearly five-hundred millimeters. As a rule most precipitation falls in the months of August and September. On an average the month of March is the driest. In March there is an average amount of rainfall of 89 millimeters. If it rains in Guam this is often in the form of showers that can sometimes be very heavy. The duration of the showers can sometimes be very short. Therefore short heavy showers of less than a minute regularly occur in Guam.


The maximum temperature in Guam is around 30-31 degrees actually throughout the year. It does not get much warmer and actually there are not many days in Guam that the temperature drops far below the limit of thirty degrees. The difference within a 24 hours’day is also not that big. The minimum temperature is between 23 and 27 degrees centigrade throughout the year. During the wetter season the temperature sensation is somewhat higher than during the drier months. This is caused by an increase of the relative air humidity through which it feels damper.

Guam lies in Typhoon Alley, an area where regularly develop tropical storms. This happens particularly in the period of July up to and including December. During that period there is a chance of Guam being struck by heavy tropical storms. Sometimes there is a question of a hurricane force that may have destructive consequences for Guam. Thus the island has been struck several times by heavy hurricanes (also called cyclones or typhoons). For instance, in 1976 the super typhoon Pamela was the cause that wooden constructions in Guam were replaced by concrete constructions. However this could not prevent the super typhoon Pongsona from causing extremely much damage in Guam in December 2002.

Climate figures
The figures below are based on registered weather information of more than one year and are an average for Guam.
(locally slight deviations may occur).

temperature (°C)


temperature (°C)
hours of sunshine

average days with precipitation
per month
per month
temperature (°C)
January 30 24 6 22 28
February 30 24 6 19 28
March 30 24 7 19 28
April 31 24 7 18 28
May 31 25 7 21 29
June 31 25 7 19 29
July 31 25 6 21 29
August 31 25 5 24 29
September 31 25 5 20 29
October 31 25 4 22 29
November 31 25 5 21 29
December 30 24 5 22 29
= 0-5 mm ● = 6-30 mm ● = 31-60 mm ● = 61-100 mm ● = 101-200 mm ● = over 200 mm
= 0-0.2 inches ● = 0.2-1.2 inches ● = 1.2-2.4 inches ● = 2.5-4 inches ● = 4.1-8 inches ● = over 8 inches

More climate information
Climate figures come in handy but do not offer an overall picture of the climate and the possible weather conditions within a particular period. You cannot often find in figures how big the chance is of wintry weather, (extreme) heat or hurricanes. Therefore we monthly offer useful extra climate information.

chance of
(very) hot


chance of
(very) cool
chance of

chance of
chance of
sunny days


click here for the explanation of the symbols


The information at this site was carefully composed from climate data collected by meteorological services, meteorological offices, climate experts and other sources. “More climate info” is based on statistics, climate data and personal experience. No rights can be derived from this site. Weather has no memory and gives no guaranties. Nothing is as changeable and unpredictable as the weather. The authors of this site feel in no way responsible for any damages caused by misinterpretation or other circumstances that may influence your holiday or trip to a certain destination. We provide information, it’s up to the reader to use it to it’s benefit.


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