September weather forecastBasel, Switzerland

The Rhine River passing through the city of Basel in Switzerland, with a view of the red stone Munster Cathedral building

September

Weather in September

September signifies the advent of the autumn season in Basel, marked by a decrease in average high temperatures to 20.3°C (68.5°F). It's also a month where rainfall experiences a decrease compared to August. As autumn colors start to show, daylight hours and sunshine duration both decline. The slight increase in relative humidity contributes to the overall fresher climate.

Temperature

A mild drop in Basel's average high-temperature is observed in September, transitioning from a warm 24.7°C (76.5°F) in August to a pleasant 20.3°C (68.5°F). In September, Basel experiences an average nighttime temperature of 10.9°C (51.6°F).

Humidity

In Basel, the average relative humidity in September is 77%.

Rainfall

In Basel, Switzerland, in September, it is raining for 8.8 days, with typically 78mm (3.07") of accumulated precipitation. Throughout the year, there are 120.4 rainfall days, and 843mm (33.19") of precipitation is accumulated.

Snowfall

May through September are months without snowfall in Basel, Switzerland.

Daylight

In September, the average length of the day in Basel, Switzerland, is 12h and 34min.
On the first day of the month, sunrise is at 06:49 and sunset at 20:09. On the last day of September, sunrise is at 07:27 and sunset at 19:10 CEST.

Sunshine

In Basel, the average sunshine in September is 5.3h.

UV index

The average daily maximum UV index in September is 5. A UV Index reading of 3 to 5 represents a moderate health risk from exposure to the Sun's UV rays for ordinary individuals.
Note: The UV index of 5 during September translates into the following guidance:
Act with care - The suggestion to avoid sunburn is emphasized. The solar radiation around mid-day is intense; avoid the Sun and stay safe. Stay sun-safe with clothing that is both closely woven and worn loosely.

Updated: Jan 24, 2024
Published by: Weather Atlas | About Us
Data Sources | Weather Forecasting & Climate

Frequently asked questions

September temperatures in Basel, Switzerland, vary between a high-temperature of 20.3°C (68.5°F) and a low-temperature of 10.9°C (51.6°F).

In September, the average relative humidity is 77%.

In Basel, Switzerland, in September, during 8.8 rainfall days, 78mm (3.07") of precipitation is typically accumulated.

May through September are months without snowfall.

In Basel, Switzerland, in September, it doesn't snow. In October, it regularly snows.

In Basel, the average day length in September is 12h and 34min.

On the first day of September in Basel, sunrise is at 06:49 and sunset at 20:09. On the last day of the month, sunrise is at 07:27 and sunset at 19:10 CEST.

The average sunshine duration in September is 5.3h.

In Basel, Switzerland, the average daily maximum UV index in September is 5. A UV Index estimate of 3 to 5 represents a moderate vulnerability from unsafe exposure to Sun's UV rays.

Today

Tomorrow

Long-term

Year J F M A M J J A September O N D

Aug

September

Oct

Average high temperature

24.7°C

20.3°C

15.2°C

Average low temperature

Average humidity

Average rainfall

Average rainfall days

Average snowfall

Average snowfall days

Average daylight

Average sunshine

Average UV index

Average temperature in September
Basel, Switzerland

Average high temperature in September: 20.3°C

The warmest month (with the highest average high temperature) is July (25.3°C).
The month with the lowest average high temperature is January (4.5°C).

Average low temperature in September: 10.9°C

The month with the highest average low temperature is July (14.5°C).
The coldest month (with the lowest average low temperature) is January (-1.1°C).

Average humidity in September
Basel, Switzerland

Average humidity in September: 77%

The months with the highest relative humidity are November and December (82%).
The month with the lowest relative humidity is April (68%).

Average rainfall in September
Basel, Switzerland

Average rainfall in September: 78mm

The wettest month (with the highest rainfall) is May (99mm).
The driest month (with the least rainfall) is February (45mm).

Average rainfall days in September
Basel, Switzerland

Average rainfall days in September: 8.8 days

The month with the highest number of rainy days is May (12.4 days).
The month with the least rainy days is February (8.4 days).

Average snowfall in September
Basel, Switzerland

Average snowfall in September: 0mm

The month with the highest snowfall is February (115mm).
The months with the least snowfall are May, June, July, August and September (0mm).

Average snowfall days in September
Basel, Switzerland

Average snowfall days in September: 0 days

The month with the highest number of snowfall days is January (3 days).
The months with the least snowfall days are May, June, July, August and September (0 days).

Average daylight in September /
Average sunshine in September
Basel, Switzerland

Average daylight in September: 12h and 36min

The month with the longest days is June (Average daylight: 15h and 54min).
The month with the shortest days is December (Average daylight: 8h and 30min).

Average sunshine in September: 5h and 18min

The month with the most sunshine is July (Average sunshine: 7h and 12min).
The month with the least sunshine is December (Average sunshine: 1h and 42min).

Average UV index in September
Basel, Switzerland

Average UV index in September: 5

The months with the highest UV index are June and July (UV index 7).
The months with the lowest UV index are January, November and December (UV index 1).