In Guam, an island administered by the United States, which is located in the western Pacific Ocean between the equator and the tropic of Cancer, and geographically is part of Micronesia, the climate is tropical, hot and humid all year round, with temperatures around 30/32 °C (86/90 °F) during the day, and 24/25 °C (75/77 °F) at night.
Here are the average temperatures of Tamuning.
Average temperatures - Tamuning

Tamuning	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
Tamuning	J	F	M	A	M	J	J	A	S	O	N	D
Min (°C)	24	24	24	25	25	25	25	25	25	25	25	25
Max (°C)	30	30	30	31	31	31	31	31	31	31	30	30
Min (°F)	75	75	75	77	77	77	77	77	77	77	77	77
Max (°F)	86	86	86	88	88	88	88	88	88	88	86	86

The rainfall is abundant, above 2,000 millimetres (79 inches) per year; the rainiest period is from July to November, the driest is from January to April, in which, however, there's no shortage of showers and thunderstorms. Here is the average precipitation.
Average precipitation - Tamuning

Tamuning	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Year
Tamuning	J	F	M	A	M	J	J	A	S	O	N	D	Y
Prec. (mm)	115	90	65	85	125	160	265	365	340	310	215	140	2275
Prec.(in)	4.5	3.5	2.6	3.3	4.9	6.3	10.4	14.4	13.4	12.2	8.5	5.5	89.6
Days	19	16	17	17	19	22	25	25	24	25	23	22	254

The amount of sunshine in Guam is never excellent, though it is acceptable or good from January to June; from July to December, during the wettest period, it is quite scarce.
Sunshine - Tamuning

Tamuning	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
Tamuning	J	F	M	A	M	J	J	A	S	O	N	D
Sun (hours)	6	7	7	7	7	6	5	5	4	4	4	5

For swimming, the sea is warm enough all year round, as can be seen in the following table.
Sea temperature - Guam

Guam	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
Guam	J	F	M	A	M	J	J	A	S	O	N	D
Sea (°C)	28	28	28	28	29	29	29	29	29	29	29	28
Sea (°F)	82	82	82	82	84	84	84	84	84	84	84	82

The island lies in the path of typhoons, tropical cyclones of Southeast Asia and the Philippine Sea. Typhoons can cause more or less serious damage, bringing heavy rains and strong winds, and occur from May to December, though they are more frequent from August to November; sometimes, however, they have passed over the island outside of this period, as happened with Roy (January 1988), Isa (April 1997), and Kong-rey (not strong, April 2007).


The best time to travel to Guam is from February to April, being the least rainy of the year, and outside of the typhoon season.


All year round, light clothes, of natural fibres, sun hat, a scarf for the breeze, a light sweatshirt for the evening; light raincoat or umbrella.
For the reef, equipment for snorkeling, water shoes or rubber soled shoes.