Grignon Weather in September
Average highs run from 19°C on September 1 to 15°C on September 30, and lows from 8°C to 5°C. Normal precipitation for the month is 85 mm over about 12 wet days.
September day by day
The normal high and low for each date, in °C.
- Normal low
- Normal high
- Reanalysis extreme high
- Reanalysis extreme low
September at a glance
- Average high
- 17°C
- Average low
- 7°C
- Precipitation
- 85 mm
- Reanalysis high
- 28°CSep 1, 2009
- Reanalysis low
- -3°CSep 26, 2002
- Daylight
- 13 h 17 min to 11 h 46 min
- Cloud cover
- 60%
- Humidity
- 74%
- Dew point
- 6°C
- Wind
- 5.4 km/h
Every day of the month
A wet day has at least 1 mm of precipitation in the reanalysis.
| Date | Normal high | Normal low | Reanalysis high | Reanalysis low | Chance wet |
|---|---|---|---|---|---|
| Sep 1 | 19°C | 8°C | 28°C 2009 | 1°C 1995 | 35% |
| Sep 2 | 19°C | 8°C | 26°C 1998 | 2°C 1992 | 35% |
| Sep 3 | 19°C | 8°C | 23°C 2004 | 4°C 1996 | 36% |
| Sep 4 | 19°C | 8°C | 25°C 2020 | 1°C 2007 | 36% |
| Sep 5 | 19°C | 8°C | 27°C 2006 | -1°C 2007 | 38% |
| Sep 6 | 18°C | 8°C | 26°C 2006 | 0°C 2007 | 38% |
| Sep 7 | 18°C | 8°C | 24°C 2016 | 3°C 2007 | 38% |
| Sep 8 | 18°C | 8°C | 23°C 2004 | 3°C 2000 | 38% |
| Sep 9 | 18°C | 7°C | 24°C 2004 | 2°C 2001 | 38% |
| Sep 10 | 18°C | 7°C | 25°C 1991 | 1°C 1996 | 39% |
| Sep 11 | 18°C | 7°C | 25°C 2018 | 0°C 2001 | 40% |
| Sep 12 | 18°C | 7°C | 24°C 2018 | 1°C 2001 | 42% |
| Sep 13 | 17°C | 7°C | 25°C 2020 | 1°C 1996 | 42% |
| Sep 14 | 17°C | 7°C | 25°C 2019 | 0°C 1996 | 41% |
| Sep 15 | 17°C | 7°C | 25°C 2019 | -1°C 2017 | 41% |
| Sep 16 | 17°C | 7°C | 25°C 2019 | 0°C 1994 | 41% |
| Sep 17 | 17°C | 7°C | 24°C 2018 | 0°C 1994 | 41% |
| Sep 18 | 17°C | 6°C | 25°C 2003 | -1°C 2001 | 41% |
| Sep 19 | 17°C | 6°C | 26°C 2003 | 0°C 2007 | 41% |
| Sep 20 | 16°C | 6°C | 26°C 2003 | 1°C 2012 | 40% |
| Sep 21 | 16°C | 6°C | 24°C 2003 | 2°C 2017 | 39% |
| Sep 22 | 16°C | 6°C | 23°C 2006 | 2°C 2014 | 38% |
| Sep 23 | 16°C | 6°C | 23°C 2018 | 1°C 2014 | 40% |
| Sep 24 | 16°C | 6°C | 23°C 1991 | -1°C 2002 | 40% |
| Sep 25 | 16°C | 6°C | 22°C 1991 | -2°C 2002 | 40% |
| Sep 26 | 16°C | 6°C | 20°C 2011 | -3°C 2002 | 40% |
| Sep 27 | 16°C | 5°C | 23°C 2018 | -2°C 2020 | 39% |
| Sep 28 | 15°C | 5°C | 21°C 2013 | 0°C 1995 | 40% |
| Sep 29 | 15°C | 5°C | 21°C 2019 | -2°C 1995 | 41% |
| Sep 30 | 15°C | 5°C | 21°C 2011 | -1°C 2015 | 42% |
Chance of rain
- Chance of a wet day
Sunrise and sunset
Times for 2026, local time (GMT+2).
- September 1
- sunrise 6:56 AM, sunset 8:13 PM
- September 30
- sunrise 7:31 AM, sunset 7:17 PM
Other months
Sources
Cloud, humidity, wind and sunshine, and temperature and precipitation: NASA POWER (MERRA-2, CERES and GEWEX SRB), 1991-2020. The data was obtained from the National Aeronautics and Space Administration (NASA) Langley Research Center's Prediction Of Worldwide Energy Resources (POWER) project funded through the NASA Earth Science Division: POWER Daily API v2, accessed 2026-09-29. Sun and moon: computed with the NOAA solar equations and Meeus.