In American Samoa, an archipelago in the Pacific Ocean located south of the equator, the climate is hot, humid and rainy throughout the year, with a maximum in rainfall from December to March, and a relative minimum from June to September.
Temperatures are stable, with little variations between the hottest period (December to April), when highs are about 31 °C (88 °F), and the coolest period (June to August) when they are around 29 °C (84 °F). Night temperatures are almost always above 20 °C (68 °F). The south-east trade winds blow steadily throughout the year, especially from May to October, and are stronger during the day, making the heat more bearable.
Here are the average temperatures of Pago Pago, the capital, located in the main island, Tutuila.
Average temperatures - Pago Pago

Pago Pago	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
Pago Pago	J	F	M	A	M	J	J	A	S	O	N	D
Min (°C)	25	25	25	25	25	25	25	25	25	25	25	25
Max (°C)	31	31	31	31	30	29	29	29	30	30	30	31
Min (°F)	77	77	77	77	77	77	77	77	77	77	77	77
Max (°F)	88	88	88	88	86	84	84	84	86	86	86	88

The rains fall in the form of downpour or thunderstorm, and usually they are intense but they don't last long, so that the sun shines quite frequently and regularly, even in the rainiest months. From December to March, however, sometimes the rains may last for the whole day.
Rainfall is enhanced by the slopes that are found in the volcanic islands (Tutuila, Ta'u, Ofu and Olosega), which, therefore, are wetter, while the small islands and the flat atolls (Aunu'u, Swains and Rose), receive less rainfall, about 2,500 millimetres (100 inches) per year. In the volcanic islands, the rainfall amount varies depending on slope exposure, so that it goes from about 3,000 mm (120 in) per year along the sheltered coasts, to 4,000 mm (160 in) per year in the coasts exposed to the trade winds; in hilly and mountainous areas it can exceed even 5,000 mm (200 in) per year.
In Pago Pago, located in Tutuila Island, 3,100 mm (122 in) of rain per year fall, with a maximum of around 370 mm (14.5 in) in December and January, and a minimum of 150/165 mm (5.9/6.3 in) between June and August. Here is the average precipitation.
Average precipitation - Pago Pago

Pago Pago	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Year
Pago Pago	J	F	M	A	M	J	J	A	S	O	N	D	Y
Prec. (mm)	365	320	295	280	270	150	165	160	195	265	285	370	3120
Prec.(in)	14,4	12,6	11,6	11	10,6	5,9	6,5	6,3	7,7	10,4	11,2	14,6	122,8
Days	24	21	24	22	20	18	19	18	18	21	21	23	249

For swimming, the sea is warm all year round, as you can see in the following table.
Sea temperature - Pago Pago

Pago Pago	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
Pago Pago	J	F	M	A	M	J	J	A	S	O	N	D
Sea (°C)	29	29	29	29	29	28	28	27	27	28	28	29
Sea (°F)	84	84	84	84	84	82	82	81	81	82	82	84

Tropical cyclones

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American Samoa is exposed to the tropical cyclones of the South Pacific. Cyclones are usually formed from November to mid-May, though they are most likely from late December to early April. Outside of this period there has been cyclone Keli, in June 1997.

When to go

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The best time to travel to American Samoa runs from June to September, being the least hot and the least rainy; anyway, even in this period, downpours and thunderstorms must be put into account.

What to pack

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All year round, tropics-friendly, loose fitting clothing, sun hat, a scarf for the breeze, a light sweatshirt for the evening, light raincoat or umbrella.