September weather forecastSaint Helier, Jersey
September
Weather in September
September initiates the transition to Autumn in Saint Helier. Despite this, temperatures remain pleasantly warm, offering an extended opportunity to enjoy the city's outdoor beauty. The rainfall volume decreases considerably from August's 42mm (1.65") to September's 31mm (1.22"). The daylight hours continue to recede, subtly signaling the arrival of shorter autumnal days. With the changing seasons, the city's scenery begins to transform, coloring the environment in fall hues.Temperature
Saint Helier's September showcases an average high-temperature of a still refreshing 17.5°C (63.5°F), hardly distinct from August's 18.2°C (64.8°F). During the nights of September, Saint Helier maintains an almost steady temperature with an average low of 15.3°C (59.5°F).Humidity
The average relative humidity in September is 79%.Rainfall
In Saint Helier, in September, during 13.3 rainfall days, 31mm (1.22") of precipitation is typically accumulated. Throughout the year, in Saint Helier, there are 189 rainfall days, and 538mm (21.18") of precipitation is accumulated.Snowfall
April through October are months without snowfall in Saint Helier.Sea temperature
In Saint Helier, in September, the average water temperature is 16°C (60.8°F).Note: In water with a temperature of 16°C (60.8°F), most people do not enjoy swimming. As the temperature descends from 21°C (69.8°F) to 15°C (59°F), breathing becomes increasingly difficult to control.
Daylight
The average length of the day in September in Saint Helier, Jersey, is 12h and 35min.On the first day of September, sunrise is at 06:25 and sunset at 19:50. On the last day of the month, sunrise is at 07:07 and sunset at 18:49 BST.
Sunshine
In September, the average sunshine is 8.6h.UV index
The months with the highest UV index are June through September, with an average maximum UV index of 5. A UV Index reading of 3 to 5 represents a moderate threat to health from unprotected exposure to Sun's UV rays for the ordinary person.Note: In September, a daily UV index of 5 turns into the following recommendations:
Make use of precautions - It is urged to ward off sun damage. The Sun's UV radiation is especially harmful around midday, so reduce exposure and stay safe. For a sun-safe wardrobe, go for clothes that are tightly woven and generously sized.
Published by: Weather Atlas | About Us
Data Sources | Weather Forecasting & Climate
Frequently asked questions
Average temperature in September
Saint Helier, Jersey
- Average high temperature in September: 17.5°C
The warmest month (with the highest average high temperature) is August (18.2°C).
The month with the lowest average high temperature is February (9°C).
- Average low temperature in September: 15.3°C
The month with the highest average low temperature is August (16.3°C).
The coldest month (with the lowest average low temperature) is February (6.8°C).
Average pressure in September
Saint Helier, Jersey
- Average pressure in September: 1018mbar
The month with the highest atmospheric pressure is September (1018mbar).
The month with the lowest atmospheric pressure is November (1011.8mbar).
Average wind speed in September
Saint Helier, Jersey
- Average wind speed in September: 23.5km/h
The windiest month (with the highest average wind speed) is December (34km/h).
The calmest month (with the lowest average wind speed) is July (20.4km/h).
Average humidity in September
Saint Helier, Jersey
- Average humidity in September: 79%
The months with the highest relative humidity are June and July (83%).
The months with the lowest relative humidity are November and December (78%).
Average rainfall in September
Saint Helier, Jersey
- Average rainfall in September: 31mm
The wettest month (with the highest rainfall) is November (78mm).
The driest month (with the least rainfall) is July (25mm).
Average rainfall days in September
Saint Helier, Jersey
- Average rainfall days in September: 13.3 days
The month with the highest number of rainy days is November (21.2 days).
The months with the least rainy days are May and July (12.2 days).
Average snowfall in September
Saint Helier, Jersey
- Average snowfall in September: 0mm
The month with the highest snowfall is January (2mm).
The months with the least snowfall are April, May, June, July, August, September and October (0mm).
Average snowfall days in September
Saint Helier, Jersey
- Average snowfall days in September: 0 days
The months with the highest number of snowfall days are January and February (0.4 days).
The months with the least snowfall days are April, May, June, July, August, September and October (0 days).
Average sea temperature in September
Saint Helier, Jersey
- Average sea temperature in September: 16°C
The best month for swimming (with the highest average sea temperature) is August (17°C).
The coldest months (with the lowest average sea temperature) are February and March (9°C).
Average daylight in September /
Average sunshine in September
Saint Helier, Jersey
- Average daylight in September: 12h and 36min
The month with the longest days is June (Average daylight: 16h and 12min).
The month with the shortest days is December (Average daylight: 8h and 18min).
- Average sunshine in September: 8h and 36min
The month with the most sunshine is July (Average sunshine: 9h and 42min).
The months with the least sunshine are January and November (Average sunshine: 4h and 0min).
Average sunshine days in September
Saint Helier, Jersey
- Average sunshine days in September: 14.2 days
The month with the most sunshine days is May (16.8 days).
The month with the least sunshine days is November (5.8 days).
Average UV index in September
Saint Helier, Jersey
- Average UV index in September: 5
The months with the highest UV index are June, July, August and September (UV index 5).
The months with the lowest UV index are January and February (UV index 2).
Average cloud cover in September
Saint Helier, Jersey
- Average cloud cover in September: 39
The months with the most cloud cover are January, November and December (Cloud cover 61).
The month with the least cloud cover is July (Cloud cover 37).
Average visibility in September
Saint Helier, Jersey
- 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).
