September weather forecastSion, Switzerland
September
Weather in September
Come September, Sion starts to transition from summer towards the autumn season, experiencing temperatures that range from 3.3°C (37.9°F) to 12.3°C (54.1°F). Despite the shortening daylight hours, the city continues to enjoy many sunny days. September can be regarded as an end to the Swiss blue-sky period before the clouds of winter start to roll in. The declining UV index makes sunbathing less risky compared to the summer months.Temperature
The start of September in Sion, Switzerland, signals a gentle decrease in the average high-temperature, transitioning from a comfortable 16.7°C (62.1°F) in August to a cool 12.3°C (54.1°F). Throughout September nights, Sion experiences a consistent temperature average of 3.3°C (37.9°F).Humidity
In September, the average relative humidity in Sion is 82%.Rainfall
The month with the least rainfall in Sion is September, when the rain falls for 20.2 days and typically collects 76mm (2.99") of precipitation.Snowfall
January through May, September through December are months with snowfall in Sion. September is the first month it typically snows. Throughout September, in the average 0.1 snowfall days, it receives 1mm (0.04") of snow. In Sion, Switzerland, during the entire year, snow falls for 40.9 days and aggregates up to 716mm (28.19") of snow.Daylight
The average length of the day in September is 12h and 32min.On the first day of September, sunrise is at 06:51 and sunset at 20:09. On the last day of the month, sunrise is at 07:28 and sunset at 19:12 CEST.
Sunshine
In Sion, the average sunshine in September is 8.3h.UV index
The average daily maximum UV index in September in Sion is 2. A UV Index of 2, and less, symbolizes a low health risk from exposure to the Sun's UV radiation for the ordinary person.Note: In September, the maximum UV index of 2 suggests these recommendations:
Children must always have sun protection, unlike most people, who can tolerate up to an hour in the sun without any burns. To prevent harmful UV exposure, minimize direct contact with the Sun around midday. Prioritize a wide-brim hat for comprehensive sun defense for your face, neck, eyes, and ears. Be cautious! The UV radiation from the Sun can be magnified almost twofold by snow reflection.
Published by: Weather Atlas | About Us
Data Sources | Weather Forecasting & Climate
Frequently asked questions
Average temperature in September
Sion, Switzerland
- Average high temperature in September: 12.3°C
The warmest month (with the highest average high temperature) is August (16.7°C).
The month with the lowest average high temperature is January (-2.5°C).
- Average low temperature in September: 3.3°C
The month with the highest average low temperature is August (6.4°C).
The coldest months (with the lowest average low temperature) are January and February (-11°C).
Average pressure in September
Sion, Switzerland
- Average pressure in September: 1018.2mbar
The month with the highest atmospheric pressure is December (1020.9mbar).
The month with the lowest atmospheric pressure is April (1015.2mbar).
Average wind speed in September
Sion, Switzerland
- Average wind speed in September: 6.5km/h
The windiest month (with the highest average wind speed) is December (8.3km/h).
The calmest month (with the lowest average wind speed) is August (6.2km/h).
Average humidity in September
Sion, Switzerland
- Average humidity in September: 82%
The month with the highest relative humidity is March (90%).
The months with the lowest relative humidity are July and August (79%).
Average rainfall in September
Sion, Switzerland
- Average rainfall in September: 76mm
The wettest month (with the highest rainfall) is May (177mm).
The driest month (with the least rainfall) is September (76mm).
Average rainfall days in September
Sion, Switzerland
- Average rainfall days in September: 20.2 days
The month with the highest number of rainy days is May (25.8 days).
The month with the least rainy days is February (13.8 days).
Average snowfall in September
Sion, Switzerland
- Average snowfall in September: 1mm
The month with the highest snowfall is February (167mm).
The months with the least snowfall are June, July and August (0mm).
Average snowfall days in September
Sion, Switzerland
- Average snowfall days in September: 0.1 days
The month with the highest number of snowfall days is February (10.2 days).
The months with the least snowfall days are June, July and August (0 days).
Average daylight in September /
Average sunshine in September
Sion, Switzerland
- Average daylight in September: 12h and 30min
The month with the longest days is June (Average daylight: 15h and 42min).
The month with the shortest days is December (Average daylight: 8h and 42min).
- Average sunshine in September: 8h and 18min
The months with the most sunshine are July and August (Average sunshine: 9h and 48min).
The month with the least sunshine is January (Average sunshine: 4h and 42min).
Average sunshine days in September
Sion, Switzerland
- Average sunshine days in September: 7.6 days
The month with the most sunshine days is October (13.5 days).
The month with the least sunshine days is June (2.8 days).
Average UV index in September
Sion, Switzerland
- Average UV index in September: 2
The months with the highest UV index are June and July (UV index 4).
The months with the lowest UV index are January and November (UV index 1).
Average cloud cover in September
Sion, Switzerland
- Average cloud cover in September: 41
The months with the most cloud cover are February and March (Cloud cover 53).
The month with the least cloud cover is October (Cloud cover 37).
Average visibility in September
Sion, Switzerland
- Average visibility in September: 7km
The months with the highest visibility are June, July, August, October and November (8km).
The months with the lowest visibility are January, February and March (6km).
