Guam's tropical climate features warm temperatures and high humidity throughout the year. There is a marked seasonal variation in rainfall, with July through December being the rainy season, although some rain occurs during the dry season. The dry season is exceptionally pleasant. The steady easterly trade winds are cool and refreshing. March is the driest month, with an average of less than 2.5 inches of rain. The average humidity varies from an early morning high of 86 percent to an afternoon low of 72 percent. The atmosphere's high moisture content during the wet season, combined with warm temperatures, contributes to the rapid deterioration of man-made materials through rust, rot and mildew.

Guam sunset At 13.6 degrees North and 145 degrees East, Guam's position is in the middle of the warm tropical waters of the Western Pacific Ocean. In comparison to other tropical locations, Guam is about 730 miles farther south than Miami and 660 miles farther south than Key West, Florida. The warm ocean waters and the abundant tropical sunshine cause Guam's climate to be warm and moist all year round. Although there may be occasions where temperatures reach the lower 90s or even the upper 60s, for the most part, daytime highs run in the lower to middle 80s and nighttime lows in the lower to middle 70s.

Of course, a very important tool every person should have on Guam is the "umbrella." It rains and rains during the "wet" season. In comparison to some stateside locations, the "dry" season is also relatively wet. Although it can still rain sometimes, the trade winds bring cooler, drier air to the island during the dry season, bringing comfortable conditions, particularly during the early morning hours. Each year, Guam averages 86 inches of rain, almost 30% higher than Miami, Florida. During 1997, parts of the island received close to 150 inches of rain - more than 12 feet of water. However, much of the heavy rain occurs during the late night and early morning hours, so the sun is still visible in the afternoon, even during the rainy season.