September weather forecast
Longwood, Saint Helena, Ascension and Tristan da Cunha

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Weather in September

Entering September, Longwood undergoes a transition from cold winters to pleasant springs, with temperatures gradually rising and wind speeds attaining their peak. Most notable in this month is the wind's gust speed, reaching its yearly maximum of 39.9km/h (24.8mph). The weather shifts are also indicated by a decrease in cloud cover, paving the way for brighter days. This month initiates a transition period preparing the residents to welcome the warmer months ahead. A blend of these weather parameters often results in spirals of colourful deciduous leaf fall painting the town.

Temperature

September tends to be the coldest month in Longwood, with temperatures averaging a daily high of 19.7°C (67.5°F) and a low of 18.7°C (65.7°F).

Humidity

The average relative humidity in September in Longwood, Saint Helena, Ascension and Tristan da Cunha, is 79%.

Rainfall

May, September through November are months with the least rain in Longwood when the rain falls for 9.6 days and typically aggregates up to 6mm (0.24") of rain.

Daylight

The average length of the day in September is 12h and 1min.
On the first day of the month, sunrise is at 06:28 and sunset at 18:16. On the last day of September, sunrise is at 06:05 and sunset at 18:19 GMT.

Sunshine

September has the least sunshine of the year, with an average of 4h of sunshine.

UV index

The months with the lowest UV index in Longwood are August through October, with an average maximum UV index of 4. A UV Index of 3 to 5 symbolizes a moderate health risk from exposure to the Sun's UV rays for ordinary individuals.
Note: In September, the average maximum UV index of 4 translates into the following recommendations:
Undertake protective steps - Recommendations to avoid sunburn are issued. The solar radiation is most powerful near the mid-day, so the exposure to the direct Sun should be reduced accordingly. A wide-brimmed hat provides unparalleled sun protection for sensitive areas like the eyes, ears, and neck.
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Frequently asked questions

What time of the year is the coldest in Longwood?

In Longwood, September is known for its average lowest temperatures, reaching a high of 19.7°C (67.5°F) and a low of 18.7°C (65.7°F).

What are the temperatures in Longwood in September?

September temperatures in Longwood, Saint Helena, Ascension and Tristan da Cunha, vary between a high-temperature of 19.7°C (67.5°F) and a low-temperature of 18.7°C (65.7°F).

What is the average humidity in September in Longwood?

In Longwood, Saint Helena, Ascension and Tristan da Cunha, the average relative humidity in September is 79%.

What is the driest month in Longwood?

May, September through November are months with the least rain in Longwood, Saint Helena, Ascension and Tristan da Cunha, when the rain falls for 9.6 days and typically aggregates up to 6mm (0.24") of rain.

How many days does it rain in September in Longwood?

In Longwood, in September, it is raining for 9.6 days, with typically 6mm (0.24") of accumulated precipitation.

How many hours of daylight does Longwood have in September?

In September, the average day length in Longwood is 12h and 1min.

When are sunrise and sunset in September in Longwood?

In September, on the first day of the month, sunrise is at 06:28 and sunset at 18:16. On the last day of the month, in Longwood, sunrise is at 06:05 and sunset at 18:19 GMT.

What is the month with the least sunshine in Longwood?

With an average of 4h of sunshine, September has the least sunshine of the year in Longwood.

How many hours of sunshine does Longwood have in September?

In Longwood, Saint Helena, Ascension and Tristan da Cunha, the average sunshine duration in September is 4h.

When is the lowest UV index in Longwood?

August through October, with an average maximum UV index of 4, are months with the lowest UV index in Longwood.

What is the UV index intensity in September in Longwood?

In September, the average daily maximum UV index is 4. A UV Index value of 3 to 5 symbolizes a medium hazard to health from unprotected exposure to UV radiation.
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Average temperature in September
Longwood, Saint Helena, Ascension and Tristan da Cunha

Average temperature in September - Longwood, Saint Helena, Ascension and Tristan da Cunha
  • Average high temperature in September: 19.7°C

The warmest month (with the highest average high temperature) is March (24.7°C).
The month with the lowest average high temperature is September (19.7°C).

  • Average low temperature in September: 18.7°C

The month with the highest average low temperature is March (23.5°C).
The coldest months (with the lowest average low temperature) are September and October (18.7°C).

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Average pressure in September
Longwood, Saint Helena, Ascension and Tristan da Cunha

Average pressure in September - Longwood, Saint Helena, Ascension and Tristan da Cunha
  • Average pressure in September: 1019mbar

The months with the highest atmospheric pressure are July and August (1019.8mbar).
The month with the lowest atmospheric pressure is February (1014.1mbar).

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Average wind speed in September
Longwood, Saint Helena, Ascension and Tristan da Cunha

Average wind speed in September - Longwood, Saint Helena, Ascension and Tristan da Cunha
  • Average wind speed in September: 28.4km/h

The windiest month (with the highest average wind speed) is September (28.4km/h).
The calmest month (with the lowest average wind speed) is January (21.8km/h).

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Average humidity in September
Longwood, Saint Helena, Ascension and Tristan da Cunha

Average humidity in September - Longwood, Saint Helena, Ascension and Tristan da Cunha
  • Average humidity in September: 79%

The month with the highest relative humidity is October (82%).
The months with the lowest relative humidity are June and July (74%).

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Average rainfall in September
Longwood, Saint Helena, Ascension and Tristan da Cunha

Average rainfall in September - Longwood, Saint Helena, Ascension and Tristan da Cunha
  • Average rainfall in September: 6mm

The wettest month (with the highest rainfall) is June (11mm).
The driest months (with the least rainfall) are May, September, October and November (6mm).

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Average rainfall days in September
Longwood, Saint Helena, Ascension and Tristan da Cunha

Average rainfall days in September - Longwood, Saint Helena, Ascension and Tristan da Cunha
  • Average rainfall days in September: 9.6 days

The month with the highest number of rainy days is June (13.6 days).
The month with the least rainy days is November (8.5 days).

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Average daylight in September /
Average sunshine in September
Longwood, Saint Helena, Ascension and Tristan da Cunha

Average daylight in September / Average sunshine in September - Longwood, Saint Helena, Ascension and Tristan da Cunha
  • Average daylight in September: 12h and 0min

The month with the longest days is December (Average daylight: 13h and 6min).
The month with the shortest days is June (Average daylight: 11h and 12min).

  • Average sunshine in September: 4h and 0min

The month with the most sunshine is February (Average sunshine: 7h and 30min).
The month with the least sunshine is September (Average sunshine: 4h and 0min).

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Average sunshine days in September
Longwood, Saint Helena, Ascension and Tristan da Cunha

Average sunshine days in September - Longwood, Saint Helena, Ascension and Tristan da Cunha
  • Average sunshine days in September: 7.7 days

The month with the most sunshine days is May (13.2 days).
The month with the least sunshine days is February (7.2 days).

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Average UV index in September
Longwood, Saint Helena, Ascension and Tristan da Cunha

Average UV index in September - Longwood, Saint Helena, Ascension and Tristan da Cunha
  • Average UV index in September: 4

The months with the highest UV index are January, February, March and May (UV index 6).
The months with the lowest UV index are August, September and October (UV index 4).

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Average cloud cover in September
Longwood, Saint Helena, Ascension and Tristan da Cunha

Average cloud cover in September - Longwood, Saint Helena, Ascension and Tristan da Cunha
  • Average cloud cover in September: 74

The month with the most cloud cover is September (Cloud cover 74).
The month with the least cloud cover is February (Cloud cover 44).

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Average visibility in September
Longwood, Saint Helena, Ascension and Tristan da Cunha

Average visibility in September - Longwood, Saint Helena, Ascension and Tristan da Cunha
  • Average visibility in September: 10km

The months with the highest visibility are January, February, March, April, May, June, July, August, September, October, November and December (10km).
The months with the lowest visibility are January, February, March, April, May, June, July, August, September, October, November and December (10km).

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Longwood, Saint Helena, Ascension and Tristan da Cunha

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