Climate averages 1991–2020
Bonn weather
in September.
A mild, moderately wet month: the 4th warmest and the 5th driest of the year.
Long-term climate patterns, not a forecast for a particular trip.
September is a mild month in Bonn: daytime highs average 19.3°C and nights cool to about 11.5°C. By daytime temperature it is the 4th warmest of the 12 months.
Expect about 62 mm of rain on roughly 11 days, which makes September a moderately wet month (the 5th driest of the 12 months). Daylight, from sunrise to sunset, lasts about 12 h 41 min on an average September day.
The nearest other city in this atlas is Troisdorf (9 km away). In September its highs average 19.2°C, about as warm as Bonn, with 68 mm of rain.
Among the 120 cities listed in Germany, Bonn ranks joint 21st of 120 for the warmest September highs and joint 48th of 120 for the driest September (rainfall, lowest first). The mean September high of those 120 cities is 18.8°C; Bonn is 0.5°C warmer than that mean.
From September to October, average highs fall by 4.8°C to 14.5°C, and monthly rainfall rises from 62 mm to 65 mm.
The annual picture
September in context
Monthly rainfall
Average total · mmAverages from hourly ERA5 reanalysis data. Actual weather varies from year to year. How these numbers are calculated
Every month, side by side
Bonn climate table
| Month | Average highHigh / low | Average low | Rainfall mm/month | Rain days ≥1 mm/day | Daylight hours/dayDaylight h/day |
|---|---|---|---|---|---|
| January | 5.4°C0.7°C | 0.7°C | 63 | 13.1 | 8.59 h |
| February | 6.6°C0.7°C | 0.7°C | 55 | 11.5 | 10.010 h |
| March | 10.3°C2.5°C | 2.5°C | 59 | 12.8 | 11.812 h |
| April | 14.5°C5.3°C | 5.3°C | 48 | 10.4 | 13.814 h |
| May | 18.3°C9.3°C | 9.3°C | 61 | 11.6 | 15.515 h |
| June | 21.3°C12.5°C | 12.5°C | 71 | 11.8 | 16.416 h |
| July | 23.4°C14.8°C | 14.8°C | 74 | 12.6 | 16.016 h |
| August | 23.2°C14.6°C | 14.6°C | 78 | 11.8 | 14.515 h |
| September, selected | 19.3°C11.5°C | 11.5°C | 62 | 10.5 | 12.713 h |
| October | 14.5°C8.3°C | 8.3°C | 65 | 11.6 | 10.811 h |
| November | 9.3°C4.6°C | 4.6°C | 66 | 12.7 | 9.09 h |
| December | 6.0°C1.7°C | 1.7°C | 75 | 14.9 | 8.18 h |
Rainfall is the average of the 30 separate monthly totals. A rain day is a local calendar day with at least 1 mm of precipitation. Daylight is the calculated sunrise-to-sunset length, not measured sunshine.
Compare places
September in nearby cities
- Troisdorf in SeptemberGermany · 9 kmHigh 19.2°C · Low 11.5°C · 68 mm rain
- Köln in SeptemberGermany · 24 kmHigh 19.1°C · Low 11.4°C · 71 mm rain
- Bergisch Gladbach in SeptemberGermany · 28 kmHigh 18.9°C · Low 11.5°C · 80 mm rain
- Leverkusen in SeptemberGermany · 34 kmHigh 19.2°C · Low 11.7°C · 71 mm rain
- Düren in SeptemberGermany · 43 kmHigh 18.7°C · Low 11.1°C · 61 mm rain
- Solingen in SeptemberGermany · 49 kmHigh 18.0°C · Low 11.0°C · 80 mm rain
- Remscheid in SeptemberGermany · 50 kmHigh 17.2°C · Low 10.2°C · 86 mm rain
- Koblenz in SeptemberGermany · 54 kmHigh 19.4°C · Low 11.4°C · 55 mm rain
Read the numbers correctly
Climate, not a promise.
These patterns help compare months. They cannot tell you the weather on a specific day of your trip.
Sources, method and limitsHow these numbers are made (what the highs, lows and rain days mean, the sources and the model cell used for Bonn) is explained once on the Bonn year overview and on the Sources, method and limits page.