Climate averages 1991–2020
Saint Helier weather
in September.
A mild, moderately wet month: the 3rd warmest and the 7th driest of the year.
Long-term climate patterns, not a forecast for a particular trip.
September is a mild month in Saint Helier: daytime highs average 17.5°C and nights cool to about 15.1°C. By daytime temperature it is the 3rd warmest of the 12 months.
Expect about 77 mm of rain on roughly 11 days, which makes September a moderately wet month (the 7th driest of the 12 months). Daylight, from sunrise to sunset, lasts about 12 h 39 min on an average September day.
The nearest other city in this atlas is Rennes (124 km away). In September its highs average 20.5°C, 3.0°C warmer than Saint Helier, with 49 mm of rain.
From September to October, average highs fall by 2.3°C to 15.2°C, and monthly rainfall rises from 77 mm to 122 mm.
The annual picture
September 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 | 18.5°C16.1°C | 16.1°C | 63 | 9.8 | 14.414 h |
| September, selected | 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
September in nearby cities
- Rennes in SeptemberFrance · 124 kmHigh 20.5°C · Low 12.2°C · 49 mm rain
- Caen in SeptemberFrance · 127 kmHigh 19.8°C · Low 12.4°C · 53 mm rain
- Le Havre in SeptemberFrance · 164 kmHigh 19.0°C · Low 13.4°C · 78 mm rain
- Poole in SeptemberUnited Kingdom · 170 kmHigh 18.0°C · Low 13.0°C · 54 mm rain
- Bournemouth in SeptemberUnited Kingdom · 171 kmHigh 17.9°C · Low 13.0°C · 54 mm rain
- Portsmouth in SeptemberUnited Kingdom · 193 kmHigh 18.3°C · Low 12.2°C · 62 mm rain
- Brest, France in SeptemberFrance · 196 kmHigh 17.8°C · Low 13.6°C · 52 mm rain
- Plymouth in SeptemberUnited Kingdom · 197 kmHigh 17.4°C · Low 12.5°C · 61 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.