Do you need to know, when is the best time to go to Saint Helena, Ascension, and Tristan da Cunha? Then you should take a look here, what weather you can expect there during the year.
The climate of Saint Helena, Ascension, and Tristan da Cunha is tropical marine. Weather is usually mild, it is tempered by the Benguela current and by winds which blow very often. Ascension island is warmer and wetter than Saint Helena island.
When speaking about the usual weather in this state, the information is relevant for example for these popular places: Ascension, Saint Helena, Tristan da Cunha.
Let's look now what weather you can expect here. (Warning: As we don't have reliable data for this country, we use data from nearby locations for these statistics.) The warmest month here is March, the average maximum temperature is 29.8 ℃ (85.64 ℉). The average minimum temperature in this month is 21.1 ℃ (69.98 ℉). The coldest month here is July, the average maximum temperature is 21 ℃ (69.8 ℉). The average minimum temperature in this month is 13.9 ℃ (57.02 ℉). 
When travelling to some places in Saint Helena, Ascension, and Tristan da Cunha, always consider the altitude of the the place as well. The highest point here is Queen Mary's Peak on Tristan da Cunha (2060 m) and the lowest point is Atlantic Ocean (0 m). So there are quite big differences in altitudes in this country, so you can expect the weather to be different in different altitudes as well. 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 Saint Helena, Ascension, and Tristan da Cunha in January is this: The average highest temperature in Saint Helena, Ascension, and Tristan da Cunha in January is 27 ℃ (80.6 ℉). The average lowest temperature is 19.6 ℃ (67.28 ℉). At the beginning of January you can expect lower temperatures, the average highest temperature is around 26.85 ℃ (80.33 ℉). At the end of January you can expect higher temperatures, the average highest temperature is around 27.75 ℃ (81.95 ℉). 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 13:00 (hours and minutes), in the middle of the month 12:55 and at the end of the month 12:46.This data is approximate because we do not have exact data for this country. It is important to say, that the weather may differ significantly in different altitudes, especially in mountains.
Typical (usual) weather in Saint Helena, Ascension, and Tristan da Cunha in February is this: The average highest temperature in Saint Helena, Ascension, and Tristan da Cunha in February is 28.5 ℃ (83.3 ℉). The average lowest temperature is 20.8 ℃ (69.44 ℉). At the beginning of February you can expect lower temperatures, the average highest temperature is around 27.75 ℃ (81.95 ℉). At the end of February you can expect higher temperatures, the average highest temperature is around 29.15 ℃ (84.47 ℉). 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 12:46 (hours and minutes), in the middle of the month 12:35 and at the end of the month 12:23.This data is approximate because we do not have exact data for this country. It is important to say, that the weather may differ significantly in different altitudes, especially in mountains.Typical (usual) weather in Saint Helena, Ascension, and Tristan da Cunha in March is this: The average highest temperature in Saint Helena, Ascension, and Tristan da Cunha in March is 29.8 ℃ (85.64 ℉). The average lowest temperature is 21.1 ℃ (69.98 ℉). At the beginning of March you can expect lower temperatures, the average highest temperature is around 29.15 ℃ (84.47 ℉). At the end of March you can expect lower temperatures, the average highest temperature is around 29.5 ℃ (85.1 ℉). 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 12:23 (hours and minutes), in the middle of the month 12:10 and at the end of the month 11:57.This data is approximate because we do not have exact data for this country. It is important to say, that the weather may differ significantly in different altitudes, especially in mountains.Typical (usual) weather in Saint Helena, Ascension, and Tristan da Cunha in April is this: The average highest temperature in Saint Helena, Ascension, and Tristan da Cunha in April is 29.2 ℃ (84.56 ℉). The average lowest temperature is 19.1 ℃ (66.38 ℉). At the beginning of April you can expect higher temperatures, the average highest temperature is around 29.5 ℃ (85.1 ℉). At the end of April you can expect lower temperatures, the average highest temperature is around 27.6 ℃ (81.68 ℉). 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 11:57 (hours and minutes), in the middle of the month 11:45 and at the end of the month 11:34.This data is approximate because we do not have exact data for this country. It is important to say, that the weather may differ significantly in different altitudes, especially in mountains.Typical (usual) weather in Saint Helena, Ascension, and Tristan da Cunha in May is this: The average highest temperature in Saint Helena, Ascension, and Tristan da Cunha in May is 26 ℃ (78.8 ℉). The average lowest temperature is 15.2 ℃ (59.36 ℉). At the beginning of May you can expect higher temperatures, the average highest temperature is around 27.6 ℃ (81.68 ℉). At the end of May you can expect lower temperatures, the average highest temperature is around 24.35 ℃ (75.83 ℉). 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 11:34 (hours and minutes), in the middle of the month 11:24 and at the end of the month 11:17.This data is approximate because we do not have exact data for this country. It is important to say, that the weather may differ significantly in different altitudes, especially in mountains.Typical (usual) weather in Saint Helena, Ascension, and Tristan da Cunha in June is this: The average highest temperature in Saint Helena, Ascension, and Tristan da Cunha in June is 22.7 ℃ (72.86 ℉). The average lowest temperature is 13.6 ℃ (56.48 ℉). At the beginning of June you can expect higher temperatures, the average highest temperature is around 24.35 ℃ (75.83 ℉). At the end of June you can expect lower temperatures, the average highest temperature is around 21.85 ℃ (71.33 ℉). 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 11:13 and at the end of the month 11:13.This data is approximate because we do not have exact data for this country. It is important to say, that the weather may differ significantly in different altitudes, especially in mountains.
Typical (usual) weather in Saint Helena, Ascension, and Tristan da Cunha in July is this: The average highest temperature in Saint Helena, Ascension, and Tristan da Cunha in July is 21 ℃ (69.8 ℉). The average lowest temperature is 13.9 ℃ (57.02 ℉). At the beginning of July you can expect higher temperatures, the average highest temperature is around 21.85 ℃ (71.33 ℉). At the end of July you can expect lower temperatures, the average highest temperature is around 21 ℃ (69.8 ℉). 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 11:13 (hours and minutes), in the middle of the month 11:17 and at the end of the month 11:25.This data is approximate because we do not have exact data for this country. It is important to say, that the weather may differ significantly in different altitudes, especially in mountains.Typical (usual) weather in Saint Helena, Ascension, and Tristan da Cunha in August is this: The average highest temperature in Saint Helena, Ascension, and Tristan da Cunha in August is 21 ℃ (69.8 ℉). The average lowest temperature is 14.7 ℃ (58.46 ℉). At the beginning of August you can expect lower temperatures, the average highest temperature is around 21 ℃ (69.8 ℉). At the end of August you can expect higher temperatures, the average highest temperature is around 22.1 ℃ (71.78 ℉). 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 11:25 (hours and minutes), in the middle of the month 11:34 and at the end of the month 11:45.This data is approximate because we do not have exact data for this country. It is important to say, that the weather may differ significantly in different altitudes, especially in mountains.Typical (usual) weather in Saint Helena, Ascension, and Tristan da Cunha in September is this: The average highest temperature in Saint Helena, Ascension, and Tristan da Cunha in September is 23.2 ℃ (73.76 ℉). The average lowest temperature is 15.8 ℃ (60.44 ℉). At the beginning of September you can expect lower temperatures, the average highest temperature is around 22.1 ℃ (71.78 ℉). At the end of September you can expect higher temperatures, the average highest temperature is around 23.45 ℃ (74.21 ℉). 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 11:45 (hours and minutes), in the middle of the month 11:57 and at the end of the month 12:10.This data is approximate because we do not have exact data for this country. It is important to say, that the weather may differ significantly in different altitudes, especially in mountains.Typical (usual) weather in Saint Helena, Ascension, and Tristan da Cunha in October is this: The average highest temperature in Saint Helena, Ascension, and Tristan da Cunha in October is 23.7 ℃ (74.66 ℉). The average lowest temperature is 16.5 ℃ (61.7 ℉). At the beginning of October you can expect lower temperatures, the average highest temperature is around 23.45 ℃ (74.21 ℉). At the end of October you can expect higher temperatures, the average highest temperature is around 24.6 ℃ (76.28 ℉). 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 12:23 and at the end of the month 12:35.This data is approximate because we do not have exact data for this country. It is important to say, that the weather may differ significantly in different altitudes, especially in mountains.Typical (usual) weather in Saint Helena, Ascension, and Tristan da Cunha in November is this: The average highest temperature in Saint Helena, Ascension, and Tristan da Cunha in November is 25.5 ℃ (77.9 ℉). The average lowest temperature is 17.3 ℃ (63.14 ℉). At the beginning of November you can expect lower temperatures, the average highest temperature is around 24.6 ℃ (76.28 ℉). At the end of November you can expect higher temperatures, the average highest temperature is around 26.1 ℃ (78.98 ℉). 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 12:35 (hours and minutes), in the middle of the month 12:46 and at the end of the month 12:55.This data is approximate because we do not have exact data for this country. It is important to say, that the weather may differ significantly in different altitudes, especially in mountains.Typical (usual) weather in Saint Helena, Ascension, and Tristan da Cunha in December is this: The average highest temperature in Saint Helena, Ascension, and Tristan da Cunha in December is 26.7 ℃ (80.06 ℉). The average lowest temperature is 17.9 ℃ (64.22 ℉). At the beginning of December you can expect lower temperatures, the average highest temperature is around 26.1 ℃ (78.98 ℉). At the end of December you can expect higher temperatures, the average highest temperature is around 26.85 ℃ (80.33 ℉). 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 12:55 (hours and minutes), in the middle of the month 13:00 and at the end of the month 13:01.This data is approximate because we do not have exact data for this country. It is important to say, that the weather may differ significantly in different altitudes, especially in mountains.