Sion Weather in September
What's the weather like in Sion (Valais) in September 2025?
The climate in Sion during September can be summarized as mild and a little damp.
September is in the fall / autumn in Sion and is typically the 4th warmest month of the year. Daytime maximum temperatures average around a cool 15°C (59°F), whilst at night 7°C (45°F) is normal.
| Daytime temperature | 14.8°C 58.6°F |
|---|---|
| Nightly temperature | 7.2°C 45°F |
| Average temperature | 11°C 51.8°F |
| Daily sunshine | 6 hrs |
| Avg rainfall | 98 mm 3.9 ins |
| Rainy days | 14 days |
| Sea temperature | 21.1°C 70.1°F |
| Humidity | 77% |
| Windspeed | 9kph 6 mph |
On average September is the 6th wettest month of the year in Sion with around 98mm 3.9 inches of rain making it a a little damp time to visit. This rainfall is typically spread over 14 days, although this may vary considerably.
On the flip side this corresponds to an average of 6 hours of sunshine per day.
September temperatures in Sion
September rainfall
September hourly sunshine
The data used in these monthly averages covers a period of over 100 years right up until last year. As such they are a valid prediction of what to expect for the weather in Sion in September 2025.
Other monthly averages
Best places to visit in September
Sion weather stats
| Hottest month: | July | 18.4°C 65.1°F |
|---|---|---|
| Driest month: | March | 78mm 3.1ins |
| Sunniest month: | July | 7.9hrs |
| Coldest month: | January | -0.5°C 31.1°F |
| Wettest month: | August | 128mm 5ins |
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