Do you need to know, when is the best time to go to American Samoa? Then you should take a look here, what weather you can expect there during the year.
The climate of American Samoa is tropical marine, but it is moderated by southeast winds. Rains are not rare here, annual rainfall averages about 3000 mm. Rainy season is from November to April, dry season from May to October. You can expect only little seasonal variation of temperatures.
When speaking about the usual weather in this state, the information is relevant for example for these popular places: National Park of American Samoa, Ofu, Olosega, Pago Pago, Ta'u, Tutuila.
Let's look now what weather you can expect in the area around the capital and in many other cities. The warmest month here is June, the average maximum temperature is 34.7 ℃ (94.46 ℉). The average minimum temperature in this month is 19.1 ℃ (66.38 ℉). The coldest month here is July, the average maximum temperature is 31.7 ℃ (89.06 ℉). The average minimum temperature in this month is 18.1 ℃ (64.58 ℉). 
When travelling to some places in American Samoa, always consider the altitude of the the place as well. The highest point here is Lata Mountain (964 m) and the lowest point is Pacific Ocean (0 m). So there are not big differences in altitudes in this country. But the altitude affects the weather even so. Keep in mind, that the temperature usually decreases by 1.2 - 1.9 ℃ (2.2 - 3.5 ℉) per 200 m (656 ft), depending on the other conditions. (And we should add, that in the very special condition named thermal inversion even the temperature may be higher in higher altitudes.)
Typical (usual) weather in American Samoa in January is this: The average highest temperature in American Samoa in January is 34.6 ℃ (94.28 ℉). The average lowest temperature is 20.9 ℃ (69.62 ℉). At the beginning of January you can expect higher temperatures, the average highest temperature is around 34.65 ℃ (94.37 ℉). At the end of January you can expect lower temperatures, the average highest temperature is around 34.4 ℃ (93.92 ℉). When planning your travel, please, keep in mind, that actual weather may differ from these average values. The length of the day at the beginning of this month is approximately 12:57 (hours and minutes), in the middle of the month 12:52 and at the end of the month 12:44.These numbers above are valid primarily for the capital and the area around it. It is important to say, that the weather may differ significantly in different altitudes.Typical (usual) weather in American Samoa in February is this: The average highest temperature in American Samoa in February is 34.2 ℃ (93.56 ℉). The average lowest temperature is 21.7 ℃ (71.06 ℉). At the beginning of February you can expect higher temperatures, the average highest temperature is around 34.4 ℃ (93.92 ℉). At the end of February you can expect lower temperatures, the average highest temperature is around 33.95 ℃ (93.11 ℉). When planning your travel, please, keep in mind, that actual weather may differ from these average values. The length of the day at the beginning of this month is approximately 12:44 (hours and minutes), in the middle of the month 12:34 and at the end of the month 12:22.These numbers above are valid primarily for the capital and the area around it. It is important to say, that the weather may differ significantly in different altitudes.Typical (usual) weather in American Samoa in March is this: The average highest temperature in American Samoa in March is 33.7 ℃ (92.66 ℉). The average lowest temperature is 21.4 ℃ (70.52 ℉). At the beginning of March you can expect higher temperatures, the average highest temperature is around 33.95 ℃ (93.11 ℉). At the end of March you can expect higher temperatures, the average highest temperature is around 34 ℃ (93.2 ℉). When planning your travel, please, keep in mind, that actual weather may differ from these average values. The length of the day at the beginning of this month is approximately 12:22 (hours and minutes), in the middle of the month 12:10 and at the end of the month 11:58.These numbers above are valid primarily for the capital and the area around it. It is important to say, that the weather may differ significantly in different altitudes.Typical (usual) weather in American Samoa in April is this: The average highest temperature in American Samoa in April is 34.3 ℃ (93.74 ℉). The average lowest temperature is 20.3 ℃ (68.54 ℉). At the beginning of April you can expect lower temperatures, the average highest temperature is around 34 ℃ (93.2 ℉). At the end of April you can expect lower temperatures, the average highest temperature is around 33.2 ℃ (91.76 ℉). When planning your travel, please, keep in mind, that actual weather may differ from these average values. The length of the day at the beginning of this month is approximately 11:58 (hours and minutes), in the middle of the month 11:46 and at the end of the month 11:36.These numbers above are valid primarily for the capital and the area around it. It is important to say, that the weather may differ significantly in different altitudes.Typical (usual) weather in American Samoa in May is this: The average highest temperature in American Samoa in May is 32.1 ℃ (89.78 ℉). The average lowest temperature is 19.9 ℃ (67.82 ℉). At the beginning of May you can expect higher temperatures, the average highest temperature is around 33.2 ℃ (91.76 ℉). At the end of May you can expect higher temperatures, the average highest temperature is around 33.4 ℃ (92.12 ℉). When planning your travel, please, keep in mind, that actual weather may differ from these average values. The length of the day at the beginning of this month is approximately 11:36 (hours and minutes), in the middle of the month 11:27 and at the end of the month 11:20.These numbers above are valid primarily for the capital and the area around it. It is important to say, that the weather may differ significantly in different altitudes.Typical (usual) weather in American Samoa in June is this: The average highest temperature in American Samoa in June is 34.7 ℃ (94.46 ℉). The average lowest temperature is 19.1 ℃ (66.38 ℉). At the beginning of June you can expect lower temperatures, the average highest temperature is around 33.4 ℃ (92.12 ℉). At the end of June you can expect lower temperatures, the average highest temperature is around 33.2 ℃ (91.76 ℉). When planning your travel, please, keep in mind, that actual weather may differ from these average values. The length of the day at the beginning of this month is approximately 11:20 (hours and minutes), in the middle of the month 11:17 and at the end of the month 11:17.These numbers above are valid primarily for the capital and the area around it. It is important to say, that the weather may differ significantly in different altitudes.Typical (usual) weather in American Samoa in July is this: The average highest temperature in American Samoa in July is 31.7 ℃ (89.06 ℉). The average lowest temperature is 18.1 ℃ (64.58 ℉). At the beginning of July you can expect higher temperatures, the average highest temperature is around 33.2 ℃ (91.76 ℉). At the end of July you can expect higher temperatures, the average highest temperature is around 32.6 ℃ (90.68 ℉). When planning your travel, please, keep in mind, that actual weather may differ from these average values. The length of the day at the beginning of this month is approximately 11:17 (hours and minutes), in the middle of the month 11:20 and at the end of the month 11:27.These numbers above are valid primarily for the capital and the area around it. It is important to say, that the weather may differ significantly in different altitudes.Typical (usual) weather in American Samoa in August is this: The average highest temperature in American Samoa in August is 33.5 ℃ (92.3 ℉). The average lowest temperature is 18.7 ℃ (65.66 ℉). At the beginning of August you can expect lower temperatures, the average highest temperature is around 32.6 ℃ (90.68 ℉). At the end of August you can expect lower temperatures, the average highest temperature is around 33.3 ℃ (91.94 ℉). When planning your travel, please, keep in mind, that actual weather may differ from these average values. The length of the day at the beginning of this month is approximately 11:27 (hours and minutes), in the middle of the month 11:36 and at the end of the month 11:47.These numbers above are valid primarily for the capital and the area around it. It is important to say, that the weather may differ significantly in different altitudes.Typical (usual) weather in American Samoa in September is this: The average highest temperature in American Samoa in September is 33.1 ℃ (91.58 ℉). The average lowest temperature is 18 ℃ (64.4 ℉). At the beginning of September you can expect higher temperatures, the average highest temperature is around 33.3 ℃ (91.94 ℉). At the end of September you can expect higher temperatures, the average highest temperature is around 33.7 ℃ (92.66 ℉). When planning your travel, please, keep in mind, that actual weather may differ from these average values. The length of the day at the beginning of this month is approximately 11:47 (hours and minutes), in the middle of the month 11:58 and at the end of the month 12:10.These numbers above are valid primarily for the capital and the area around it. It is important to say, that the weather may differ significantly in different altitudes.Typical (usual) weather in American Samoa in October is this: The average highest temperature in American Samoa in October is 34.3 ℃ (93.74 ℉). The average lowest temperature is 20.4 ℃ (68.72 ℉). At the beginning of October you can expect lower temperatures, the average highest temperature is around 33.7 ℃ (92.66 ℉). At the end of October you can expect lower temperatures, the average highest temperature is around 34.3 ℃ (93.74 ℉). When planning your travel, please, keep in mind, that actual weather may differ from these average values. The length of the day at the beginning of this month is approximately 12:10 (hours and minutes), in the middle of the month 12:22 and at the end of the month 12:33.These numbers above are valid primarily for the capital and the area around it. It is important to say, that the weather may differ significantly in different altitudes.Typical (usual) weather in American Samoa in November is this: The average highest temperature in American Samoa in November is 34.3 ℃ (93.74 ℉). The average lowest temperature is 20.7 ℃ (69.26 ℉). At the beginning of November you can expect lower temperatures, the average highest temperature is around 34.3 ℃ (93.74 ℉). At the end of November you can expect higher temperatures, the average highest temperature is around 34.5 ℃ (94.1 ℉). When planning your travel, please, keep in mind, that actual weather may differ from these average values. The length of the day at the beginning of this month is approximately 12:33 (hours and minutes), in the middle of the month 12:44 and at the end of the month 12:52.These numbers above are valid primarily for the capital and the area around it. It is important to say, that the weather may differ significantly in different altitudes.Typical (usual) weather in American Samoa in December is this: The average highest temperature in American Samoa in December is 34.7 ℃ (94.46 ℉). The average lowest temperature is 20.1 ℃ (68.18 ℉). At the beginning of December you can expect lower temperatures, the average highest temperature is around 34.5 ℃ (94.1 ℉). At the end of December you can expect lower temperatures, the average highest temperature is around 34.65 ℃ (94.37 ℉). When planning your travel, please, keep in mind, that actual weather may differ from these average values. The length of the day at the beginning of this month is approximately 12:52 (hours and minutes), in the middle of the month 12:57 and at the end of the month 12:58.These numbers above are valid primarily for the capital and the area around it. It is important to say, that the weather may differ significantly in different altitudes.