Climate averages 1991–2020
Saint Helier weather
in August.
A mild, moderately wet month: the warmest and the 5th driest of the year.
Long-term climate patterns, not a forecast for a particular trip.
August is a mild month in Saint Helier: daytime highs average 18.5°C and nights cool to about 16.1°C. By daytime temperature it is the warmest month of the year.
Expect about 63 mm of rain on roughly 10 days, which makes August a moderately wet month (the 5th driest of the 12 months). Daylight, from sunrise to sunset, lasts about 14 h 24 min on an average August day.
The nearest other city in this atlas is Rennes (124 km away). In August its highs average 23.2°C, 4.7°C warmer than Saint Helier, with 46 mm of rain.
From August to September, average highs fall by 1.0°C to 17.5°C, and monthly rainfall rises from 63 mm to 77 mm.
The annual picture
August in context
Monthly rainfall
Average total · mmAverages from hourly ERA5 reanalysis data. Actual weather varies from year to year. How these numbers are calculated
Every month, side by side
Saint Helier climate table
| Month | Average highHigh / low | Average low | Rainfall mm/month | Rain days ≥1 mm/day | Daylight hours/dayDaylight h/day |
|---|---|---|---|---|---|
| January | 9.1°C6.8°C | 6.8°C | 110 | 15.8 | 8.79 h |
| February | 8.7°C6.3°C | 6.3°C | 82 | 13.0 | 10.110 h |
| March | 9.7°C7.3°C | 7.3°C | 69 | 12.4 | 11.912 h |
| April | 11.3°C8.6°C | 8.6°C | 57 | 10.5 | 13.714 h |
| May | 13.7°C11.0°C | 11.0°C | 53 | 9.4 | 15.315 h |
| June | 16.1°C13.4°C | 13.4°C | 50 | 8.7 | 16.216 h |
| July | 17.9°C15.4°C | 15.4°C | 48 | 9.1 | 15.816 h |
| August, selected | 18.5°C16.1°C | 16.1°C | 63 | 9.8 | 14.414 h |
| September | 17.5°C15.1°C | 15.1°C | 77 | 11.0 | 12.713 h |
| October | 15.2°C12.9°C | 12.9°C | 122 | 15.5 | 10.811 h |
| November | 12.2°C10.0°C | 10.0°C | 132 | 17.6 | 9.29 h |
| December | 10.0°C7.7°C | 7.7°C | 138 | 16.7 | 8.38 h |
Rainfall is the average of the 30 separate monthly totals. A rain day is a local calendar day with at least 1 mm of precipitation. Daylight is the calculated sunrise-to-sunset length, not measured sunshine.
Compare places
August in nearby cities
- Rennes in AugustFrance · 124 kmHigh 23.2°C · Low 14.3°C · 46 mm rain
- Caen in AugustFrance · 127 kmHigh 22.6°C · Low 14.5°C · 60 mm rain
- Le Havre in AugustFrance · 164 kmHigh 21.2°C · Low 15.3°C · 73 mm rain
- Poole in AugustUnited Kingdom · 170 kmHigh 20.0°C · Low 14.6°C · 63 mm rain
- Bournemouth in AugustUnited Kingdom · 171 kmHigh 20.0°C · Low 14.6°C · 63 mm rain
- Portsmouth in AugustUnited Kingdom · 193 kmHigh 20.6°C · Low 14.1°C · 64 mm rain
- Brest, France in AugustFrance · 196 kmHigh 19.1°C · Low 14.9°C · 53 mm rain
- Plymouth in AugustUnited Kingdom · 197 kmHigh 19.4°C · Low 14.1°C · 69 mm rain
Read the numbers correctly
Climate, not a promise.
These patterns help compare months. They cannot tell you the weather on a specific day of your trip.
Sources, method and limitsHow these numbers are made (what the highs, lows and rain days mean, the sources and the model cell used for Saint Helier) is explained once on the Saint Helier year overview and on the Sources, method and limits page.