Ottawa Weather in September
Average highs run from 24°C on September 1 to 17°C on September 30, and lows from 12°C to 7°C. Normal precipitation for the month is 87 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
- 21°C
- Average low
- 10°C
- Precipitation
- 87 mm
- Reanalysis high
- 33°CSep 9, 2002
- Reanalysis low
- -2°CSep 30, 1991
- Daylight
- 13 h 16 min to 11 h 45 min
- Cloud cover
- 58%
- Humidity
- 78%
- Dew point
- 11°C
- Wind
- 6.8 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 | 24°C | 12°C | 32°C 2010 | 6°C 2017 | 40% |
| Sep 2 | 24°C | 12°C | 31°C 2008 | 5°C 1992 | 41% |
| Sep 3 | 23°C | 12°C | 32°C 1999 | 4°C 1994 | 40% |
| Sep 4 | 23°C | 12°C | 32°C 1999 | 5°C 1994 | 40% |
| Sep 5 | 23°C | 12°C | 30°C 2018 | 5°C 2000 | 41% |
| Sep 6 | 23°C | 11°C | 30°C 2016 | 5°C 2013 | 41% |
| Sep 7 | 23°C | 11°C | 32°C 2016 | 6°C 1995 | 42% |
| Sep 8 | 23°C | 11°C | 32°C 2002 | 3°C 1995 | 42% |
| Sep 9 | 22°C | 11°C | 33°C 2002 | 5°C 2019 | 44% |
| Sep 10 | 22°C | 11°C | 32°C 2002 | 4°C 1995 | 43% |
| Sep 11 | 22°C | 10°C | 28°C 2003 | 4°C 1995 | 42% |
| Sep 12 | 22°C | 10°C | 30°C 2005 | 3°C 1992 | 40% |
| Sep 13 | 22°C | 10°C | 29°C 2005 | 5°C 1991 | 41% |
| Sep 14 | 21°C | 10°C | 29°C 2005 | 5°C 2013 | 41% |
| Sep 15 | 21°C | 10°C | 29°C 2018 | 3°C 1995 | 41% |
| Sep 16 | 21°C | 9°C | 29°C 2018 | 3°C 2007 | 41% |
| Sep 17 | 21°C | 9°C | 29°C 2018 | 3°C 2013 | 41% |
| Sep 18 | 21°C | 9°C | 28°C 2015 | 1°C 2014 | 41% |
| Sep 19 | 20°C | 9°C | 27°C 2017 | -1°C 2014 | 41% |
| Sep 20 | 20°C | 9°C | 28°C 2002 | 0°C 1993 | 43% |
| Sep 21 | 20°C | 9°C | 28°C 1998 | 1°C 1991 | 43% |
| Sep 22 | 20°C | 9°C | 26°C 2007 | 2°C 1991 | 43% |
| Sep 23 | 20°C | 8°C | 29°C 2017 | 3°C 1992 | 43% |
| Sep 24 | 19°C | 8°C | 29°C 2017 | 0°C 1997 | 43% |
| Sep 25 | 19°C | 8°C | 29°C 2017 | 0°C 2000 | 43% |
| Sep 26 | 19°C | 8°C | 29°C 2017 | 2°C 2009 | 43% |
| Sep 27 | 18°C | 8°C | 28°C 2017 | 3°C 2000 | 45% |
| Sep 28 | 18°C | 7°C | 26°C 1999 | -2°C 2000 | 46% |
| Sep 29 | 18°C | 7°C | 25°C 1999 | -1°C 2000 | 46% |
| Sep 30 | 17°C | 7°C | 22°C 2013 | -2°C 1991 | 46% |
Chance of rain
- Chance of a wet day
Sunrise and sunset
Times for 2026, local time (EDT).
- September 1
- sunrise 6:24 AM, sunset 7:40 PM
- September 30
- sunrise 7:00 AM, sunset 6:45 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 2026-09-24. Sun and moon: computed with the NOAA solar equations and Meeus.