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Jamestown, Saint Helena climate
BSh Hot semi-arid
Jamestown has a remarkably steady warm-temperate climate (Hot semi-arid, Köppen BSh). The hottest month is March with an average daily high near 24°C, while the coldest is August averaging around 14°C at night. Around 428 mm of precipitation falls each year, peaking in June (50 mm) and easing off in November (17 mm).
Temperature & precipitation
Daily high–low temperature range with the monthly average, plus monthly precipitation · 1991–2020 normals · hover a month for the exact figuresHours of sunshine per day
Estimated sunny hours each month — daylight length × clear-sky fraction · 1991–2020 monthly cloud cover (NASA POWER)Jamestown climate normals (1991–2020)
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Avg high (°C) | 22 | 23 | 24 | 23 | 22 | 20 | 19 | 18 | 18 | 18 | 19 | 21 |
| Avg temp (°C) | 20 | 21 | 21 | 21 | 20 | 18 | 17 | 16 | 16 | 17 | 17 | 19 |
| Avg low (°C) | 18 | 19 | 19 | 19 | 18 | 16 | 15 | 14 | 14 | 15 | 15 | 16 |
| Precipitation (mm) | 30 | 38 | 48 | 40 | 31 | 50 | 46 | 46 | 36 | 25 | 17 | 21 |
| Jan – Jun | Jan | Feb | Mar | Apr | May | Jun |
|---|---|---|---|---|---|---|
| Avg high (°C) | 22 | 23 | 24 | 23 | 22 | 20 |
| Avg temp (°C) | 20 | 21 | 21 | 21 | 20 | 18 |
| Avg low (°C) | 18 | 19 | 19 | 19 | 18 | 16 |
| Precipitation (mm) | 30 | 38 | 48 | 40 | 31 | 50 |
| Jul – Dec | Jul | Aug | Sep | Oct | Nov | Dec |
|---|---|---|---|---|---|---|
| Avg high (°C) | 19 | 18 | 18 | 18 | 19 | 21 |
| Avg temp (°C) | 17 | 16 | 16 | 17 | 17 | 19 |
| Avg low (°C) | 15 | 14 | 14 | 15 | 15 | 16 |
| Precipitation (mm) | 46 | 46 | 36 | 25 | 17 | 21 |
Sky & atmosphere
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Cloud cover (%) | 59 | 52 | 54 | 56 | 54 | 62 | 67 | 79 | 82 | 83 | 78 | 70 |
| Relative humidity (%) | 78 | 77 | 77 | 76 | 75 | 73 | 73 | 75 | 78 | 80 | 79 | 78 |
| Wind speed (km/h) | 19.0 | 19.1 | 19.9 | 20.3 | 19.8 | 21.1 | 21.7 | 22.7 | 22.5 | 22.3 | 21.3 | 19.6 |
| Jan – Jun | Jan | Feb | Mar | Apr | May | Jun |
|---|---|---|---|---|---|---|
| Cloud cover (%) | 59 | 52 | 54 | 56 | 54 | 62 |
| Relative humidity (%) | 78 | 77 | 77 | 76 | 75 | 73 |
| Wind speed (km/h) | 19.0 | 19.1 | 19.9 | 20.3 | 19.8 | 21.1 |
| Jul – Dec | Jul | Aug | Sep | Oct | Nov | Dec |
|---|---|---|---|---|---|---|
| Cloud cover (%) | 67 | 79 | 82 | 83 | 78 | 70 |
| Relative humidity (%) | 73 | 75 | 78 | 80 | 79 | 78 |
| Wind speed (km/h) | 21.7 | 22.7 | 22.5 | 22.3 | 21.3 | 19.6 |
Methodology & sources
Temperature & precipitation — 1991–2020 normals computed from 30 years of daily observations at St. Helena Is., a weather station, about 6 km from the city centre. The underlying daily records come from NOAA's global station network.
Cloud, humidity, wind & sunshine — modelled estimates from NASA POWER, NASA's satellite-and-reanalysis climatology. This is the standard global source for atmospheric variables, which are not measured at most weather stations.