Climate averages 1991–2020
Boulogne-Billancourt weather
in September.
A mild, moderately wet month: the 4th warmest and the driest of the year.
Long-term climate patterns, not a forecast for a particular trip.
September is a mild month in Boulogne-Billancourt: daytime highs average 20.7°C and nights cool to about 12.3°C. By daytime temperature it is the 4th warmest of the 12 months.
Expect about 47 mm of rain on roughly 8 days, which makes September a moderately wet month (the driest month of the year). Daylight, from sunrise to sunset, lasts about 12 h 39 min on an average September day.
The nearest other city in this atlas is Paris 15 Vaugirard (4 km away). In September its highs average 20.7°C, about as warm as Boulogne-Billancourt, with 47 mm of rain.
Among the 57 cities listed in France, Boulogne-Billancourt ranks joint 27th of 57 for the warmest September highs and joint 4th of 57 for the driest September (rainfall, lowest first). The mean September high of those 57 cities is 21.3°C; Boulogne-Billancourt is 0.6°C cooler than that mean.
From September to October, average highs fall by 4.5°C to 16.1°C, and monthly rainfall rises from 47 mm to 62 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
Boulogne-Billancourt climate table
| Month | Average highHigh / low | Average low | Rainfall mm/month | Rain days ≥1 mm/day | Daylight hours/dayDaylight h/day |
|---|---|---|---|---|---|
| January | 7.3°C2.3°C | 2.3°C | 52 | 11.3 | 8.89 h |
| February | 8.4°C2.1°C | 2.1°C | 48 | 10.0 | 10.110 h |
| March | 11.9°C4.0°C | 4.0°C | 50 | 10.5 | 11.912 h |
| April | 15.1°C6.3°C | 6.3°C | 50 | 10.6 | 13.714 h |
| May | 18.6°C9.9°C | 9.9°C | 66 | 11.3 | 15.215 h |
| June | 21.8°C13.1°C | 13.1°C | 57 | 10.6 | 16.116 h |
| July | 24.1°C15.2°C | 15.2°C | 55 | 9.4 | 15.716 h |
| August | 24.2°C15.2°C | 15.2°C | 56 | 9.0 | 14.414 h |
| September, selected | 20.7°C12.3°C | 12.3°C | 47 | 8.3 | 12.613 h |
| October | 16.1°C9.5°C | 9.5°C | 62 | 11.2 | 10.911 h |
| November | 10.8°C5.6°C | 5.6°C | 58 | 11.3 | 9.29 h |
| December | 7.7°C2.9°C | 2.9°C | 68 | 12.5 | 8.38 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
- Paris 15 Vaugirard in SeptemberFrance · 4 kmHigh 20.7°C · Low 12.1°C · 47 mm rain
- Paris in SeptemberFrance · 8 kmHigh 20.6°C · Low 11.9°C · 47 mm rain
- Paris 13 Gobelins in SeptemberFrance · 8 kmHigh 20.6°C · Low 11.9°C · 47 mm rain
- Versailles in SeptemberFrance · 9 kmHigh 20.0°C · Low 11.6°C · 47 mm rain
- Paris 20 Ménilmontant in SeptemberFrance · 12 kmHigh 20.3°C · Low 11.6°C · 48 mm rain
- Argenteuil in SeptemberFrance · 13 kmHigh 20.6°C · Low 12.1°C · 44 mm rain
- Créteil in SeptemberFrance · 17 kmHigh 20.7°C · Low 12.1°C · 48 mm rain
- Saint-Quentin-en-Yvelines in SeptemberFrance · 18 kmHigh 19.9°C · Low 11.3°C · 48 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 Boulogne-Billancourt) is explained once on the Boulogne-Billancourt year overview and on the Sources, method and limits page.
Paris, Paris 15 Vaugirard and Paris 13 Gobelins lie in the same rainfall cell, so their rainfall figures are identical to these; temperatures differ because they come from smaller 0.1° cells.