September weather forecastBonn, Germany
September
Weather in September
The climes in Bonn begin to cool down entering September, signaling the onset of the Autumn season. Temperatures slide down to more comfortable levels, providing relief from the scorching heat of the summer months. The frequency of rainfall subsides and the city witnesses showers less frequently than in August. This reduction in rain heightens the visibility, making outdoor activity increasingly appealing. Although the long summer days are replaced by shorter daylight hours, September brings unique charm and beauty as leaves change their color.Temperature
September signals a slight drop in average high-temperature, sliding from August's warm 23.3°C (73.9°F) to an enjoyable 18.9°C (66°F). Bonn's average low-temperature during September nights is observed to be a frosty 9.8°C (49.6°F).Humidity
In September, the average relative humidity is 78%.Rainfall
April and September are months with the least rain in Bonn when the rain falls for 10.5 days and typically aggregates up to 17mm (0.67") of rain.Snowfall
In Bonn, snow does not fall in April through October.Daylight
In September, the average length of the day is 12h and 37min.On the first day of September in Bonn, Germany, sunrise is at 06:46 and sunset at 20:16. On the last day of the month, sunrise is at 07:31 and sunset at 19:11 CEST.
Sunshine
In Bonn, the average sunshine in September is 8.4h.UV index
In September, the average daily maximum UV index is 4. A UV Index value of 3 to 5 symbolizes a medium vulnerability from unsafe exposure to UV radiation for ordinary individuals.Note: In September, the maximum UV index of 4 translates into these guidelines:
Undertake protective steps - Recommendations to avoid sunburn are issued. The solar radiation is most powerful near the mid-day, so the exposure to the direct Sun should be reduced accordingly. For effective sun eye protection, rely on sunglasses certified for UVA and UVB resistance.
Published by: Weather Atlas | About Us
Data Sources | Weather Forecasting & Climate
Frequently asked questions
Average temperature in September
Bonn, Germany
- Average high temperature in September: 18.9°C
The warmest month (with the highest average high temperature) is July (23.5°C).
The month with the lowest average high temperature is January (4°C).
- Average low temperature in September: 9.8°C
The month with the highest average low temperature is August (13.3°C).
The coldest month (with the lowest average low temperature) is January (-0.3°C).
Average pressure in September
Bonn, Germany
- Average pressure in September: 1017.8mbar
The month with the highest atmospheric pressure is September (1017.8mbar).
The month with the lowest atmospheric pressure is November (1013.6mbar).
Average wind speed in September
Bonn, Germany
- Average wind speed in September: 9.1km/h
The windiest month (with the highest average wind speed) is February (12.8km/h).
The calmest month (with the lowest average wind speed) is August (8.9km/h).
Average humidity in September
Bonn, Germany
- Average humidity in September: 78%
The month with the highest relative humidity is December (89%).
The months with the lowest relative humidity are July and August (73%).
Average rainfall in September
Bonn, Germany
- Average rainfall in September: 17mm
The wettest month (with the highest rainfall) is August (33mm).
The driest months (with the least rainfall) are April and September (17mm).
Average rainfall days in September
Bonn, Germany
- Average rainfall days in September: 10.5 days
The month with the highest number of rainy days is July (15.6 days).
The month with the least rainy days is February (10.4 days).
Average snowfall in September
Bonn, Germany
- Average snowfall in September: 0mm
The month with the highest snowfall is February (35mm).
The months with the least snowfall are April, May, June, July, August, September and October (0mm).
Average snowfall days in September
Bonn, Germany
- Average snowfall days in September: 0 days
The month with the highest number of snowfall days is January (6 days).
The months with the least snowfall days are May, June, July, August, September and October (0 days).
Average daylight in September /
Average sunshine in September
Bonn, Germany
- Average daylight in September: 12h and 36min
The month with the longest days is June (Average daylight: 16h and 24min).
The month with the shortest days is December (Average daylight: 8h and 6min).
- Average sunshine in September: 8h and 24min
The month with the most sunshine is July (Average sunshine: 9h and 54min).
The month with the least sunshine is December (Average sunshine: 3h and 48min).
Average sunshine days in September
Bonn, Germany
- Average sunshine days in September: 16.4 days
The month with the most sunshine days is October (16.5 days).
The month with the least sunshine days is December (11.4 days).
Average UV index in September
Bonn, Germany
- Average UV index in September: 4
The months with the highest UV index are June and July (UV index 5).
The months with the lowest UV index are January, February, November and December (UV index 2).
Average cloud cover in September
Bonn, Germany
- Average cloud cover in September: 40
The month with the most cloud cover is December (Cloud cover 62).
The month with the least cloud cover is August (Cloud cover 37).
Average visibility in September
Bonn, Germany
- Average visibility in September: 8km
The months with the highest visibility are March, April, May, June, July and August (9km).
The months with the lowest visibility are January, February, September, October, November and December (8km).
