Guam - The climate in short
In Guam, the climate is tropical, hot and humid all year round, with a relatively dry period from January to May, and a rainy period from July to November. June and December are transition months.
Guam is an island administered by the United States and located in the western Pacific Ocean, about 2,000 kilometers (1,200 miles) east of the Philippines, between the Equator and the Tropic of Cancer (at 13 degrees north latitude); geographically, it is part of Micronesia.
The climate in detail
Tamuning
Temperatures are very stable, and are around 30/31.5 °C (86/89 °F) during the day and 23.5/25 °C (74/77 °F) at night, all year round.
Given the enormous distance from the continents, temperatures vary little compared to the averages. At night, it never gets cold. On cooler nights, the temperature typically drops to 21/22 °C (70/72 °F) from December to March, although it can drop down to 18/19 °C (64/66 °F) from time to time. On the hottest days, the temperature reaches 33/34 °C (91/93 °F), and this usually happens in April and May.
Here are the average temperatures at the international airport, located near
Tamuning.
Tamuning - Average temperatures (1991-2020) | Month | Min (°C) | Max (°C) | Mean (°C) | Min (°F) | Max (°F) | Mean (°F) |
|---|
| January | 23.8 | 29.9 | 26.9 | 75 | 86 | 80.3 |
|---|
| February | 23.6 | 29.9 | 26.8 | 75 | 86 | 80.2 |
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| March | 24 | 30.5 | 27.2 | 75 | 87 | 81.1 |
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| April | 24.8 | 31.2 | 28 | 77 | 88 | 82.4 |
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| May | 25.3 | 31.4 | 28.4 | 78 | 89 | 83.1 |
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| June | 25.4 | 31.5 | 28.5 | 78 | 89 | 83.3 |
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| July | 24.9 | 31.1 | 28 | 77 | 88 | 82.4 |
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| August | 24.6 | 30.7 | 27.6 | 76 | 87 | 81.7 |
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| September | 24.5 | 30.7 | 27.6 | 76 | 87 | 81.7 |
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| October | 24.7 | 30.9 | 27.8 | 76 | 88 | 82 |
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| November | 25 | 30.9 | 28 | 77 | 88 | 82.3 |
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| December | 24.7 | 30.4 | 27.6 | 76 | 87 | 81.6 |
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| Year | 24.6 | 30.8 | 27.65 | 76.3 | 87.4 | 81.5 |
|---|
The
rainfall is abundant, above 2,000 millimeters (80 inches) per year; the rainiest period is from July to November, while the driest one is from February to May, when, however, showers often occur, although they usually do not last long. The humidity is high all year round, but especially in the wettest period: from July to November, the average is equal to or higher than 80%, while from February to May, it drops to about 75%.
Here is the average precipitation.
Tamuning - Average precipitation| Month | Millimeters | Inches | Days |
|---|
| January | 135 | 5.3 | 20 |
|---|
| February | 100 | 3.9 | 18 |
|---|
| March | 70 | 2.8 | 18 |
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| April | 90 | 3.5 | 18 |
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| May | 110 | 4.3 | 18 |
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| June | 155 | 6.1 | 21 |
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| July | 265 | 10.4 | 23 |
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| August | 420 | 16.5 | 25 |
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| September | 380 | 15 | 25 |
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| October | 315 | 12.4 | 25 |
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| November | 200 | 7.9 | 22 |
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| December | 135 | 5.3 | 22 |
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| Year | 2370 | 93.3 | 255 |
|---|
The amount of
sunshine in Guam is not excellent, since it amounts to about 2,000 hours per year, though it is acceptable or good from February to June; from July to December, during the wettest period, it is quite scarce.
Here are the average sunshine hours per day.
Tamuning - Sunshine hours| Month | Average | Total |
|---|
January | 5.5 | 175 | February | 6 | 175 | March | 7 | 215 | April | 7 | 215 | May | 7 | 220 | June | 6.5 | 195 | July | 5 | 155 | August | 4.5 | 140 | September | 4.5 | 135 | October | 4.5 | 135 | November | 4.5 | 135 | December | 4.5 | 145 | Year | 5.6 | 2035 |
Sea temperature
The sea in Guam is warm enough to swim in all year round, as can be seen in the following table.
Tamuning - Sea temperature| Month | Celsius (°C) | Fahrenheit (°F) |
|---|
January | 28 | 82 | February | 27.5 | 82 | March | 27.5 | 82 | April | 28 | 83 | May | 29 | 84 | June | 29.5 | 85 | July | 29.5 | 85 | August | 29.5 | 85 | September | 29.5 | 85 | October | 29.5 | 85 | November | 29 | 84 | December | 28.5 | 83 | Year | 28.8 | 83.9 |
Tropical cyclones
The island lies in the path of
typhoons, the tropical cyclones of Southeast Asia and the Philippine Sea. Typhoons can cause more or less serious damage, bringing heavy rains and strong winds, and normally occur from May to December, though they are more frequent from August to November. Sometimes, however, they have affected the island outside of this period, as happened with typhoon Roy (in January 1988), Isa (in April 1997), and Kong-rey (not strong, in April 2007).
When to go
The best time to travel to Guam is from
February to April, since it is the least rainy period of the year, and (normally) outside of the typhoon season.
What to pack
All year round, bring
light clothes of natural fibers, a sun hat, a scarf for the breeze, a light sweatshirt for the evening, and a light raincoat or umbrella.
When going to the reef, you can bring snorkeling equipment, including water shoes or rubber-soled shoes.
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