Climate of Guam

Climate of Guam

Guam is an island in Oceania. The 549 square kilometer Guam is not an independent country, but a separate territory of the United States of America. Guam belongs to the region of Micronesia.

Guam has a tropical rainforest climate, which is indicated by the letter code Af within the Köppen-Geiger climate classification. Guam has a drier season and a wet season. This wet season starts in July and lasts through November. During this period, the precipitation amounts per month can easily rise to three hundred, and in some years even to five hundred millimeters per month. As a rule, most precipitation falls in the months of August and September. On average, March is the driest month. In March there is an average of 89 millimeters of rain. When it rains on Guam, it is often in the form of showers, which can sometimes be very strong and short. Short downpours of less than a minute are therefore regular on Guam.


The maximum temperature on Guam is actually around 30-31 degrees all year round. It doesn’t get much warmer and days when the mercury drops far below the limit of thirty degrees, do not actually occur on Guam. The difference within 24 hours is also not that great. The minimum temperature is between 23 and 27 degrees Celsius all year round. During the wetter season, the perceived temperature is somewhat higher than during the drier months. This is due to an increase in relative humidity, which makes it feel clammier.


Guam is located in Typhoon Alley, an area where tropical storms regularly occur. This mainly happens in the period from July to December. There is a chance that Guam will be hit by severe tropical storms during that period. At times, hurricane-force winds can have devastating effects on Guam. For example, the island has been hit several times by severe hurricanes (also called cyclones or typhoons). For example, super typhoon Pamela in 1976 was the reason to replace wooden structures on Guam with concrete structures. However, that did not prevent super typhoon Pongsona in December 2002 from causing enormous damage to Guam.

Climate figures

The figures below are based on long-term average climate statistics. The temperatures are displayed in degrees Celsius (°C).

Maximum temperature Minimum temperature Hours of sunshine per day Days of rainfall per month Water temperature
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℃

Best time to visit Guam

Do you want to know when is the best time to travel to Guam? You can determine the best time to travel to a destination based on the weather and climate. In addition, there are other factors that are not directly related to the weather and that can influence the best travel periods for a travel destination. Think, for example, of holidays or festive periods, which makes traveling more interesting or not, because daily life comes to a standstill as a result. Guam is an island in Oceania that is a separate territory from the United States. For the Americans, this island is of strategic importance. A large naval and air force base is located there. In addition to the approximately six thousand American military personnel, Guam is also simply the homeland for almost two hundred thousand inhabitants. Guam has a tropical rainforest climate with the driest month of March being slightly wet to create a tropical monsoon climate. There is clearly a dry season and a wet season.

Best months

The dry season starts in mid-January and lasts until early May. Within this period you can indicate the months of February, March and April as the best time to travel to Guam. These are the three driest months of the year. The afternoon temperature is then around 30-31 degrees Celsius. During the first five to six months there is a fairly strong east trade that can provide the necessary cooling. Once the wetter season has started, the chances of rain increase considerably. Showers become more frequent, are often heavier and are often accompanied by thunderstorms. You notice that from July to October the wind will blow more often from other directions. The eastern direction is then no longer dominant and the wind blows more often from the southern and western corners. What you especially notice during the rainy season is that the air can be uncomfortably damp.

The hurricane

Guam is located in an area where typhoons (hurricanes) can pass or pass. Heavy precipitation and lashing winds, sometimes reaching speeds of over 200 kilometers per hour, can cause significant damage to islands such as Guam. Fortunately, the passing of a hurricane is not an annual phenomenon. Hurricanes are most likely to occur during hurricane season, which runs from approximately July through November. Hurricanes can happen out of season, but they are rarely very strong.