When to Go
Peak Season: January to May
Guam gets tourists year-round, especially during winter in Japan. Peak Season temperatures hover in the mid 80s and humidity is tolerable.
Off Season: July to November
Rainy season in Guam still brings plenty of sunshine (would you expect anything less in paradise?) and hotel rates at their lowest. Do be careful of heavy winds leading up to typhoons.
Shoulder Season: June, December
There isn't really a shoulder season in Guam and weather during June and December varies from year to year; some years both months are dry and other years you'll get soaked.