Ottawa Weather in September
Average highs run from 85°F on September 1 to 75°F on September 30, and lows from 61°F to 50°F. Normal precipitation for the month is 4.05 in over about 8 wet days.
September day by day
The normal high and low for each date, and the record, in °F.
- Normal low
- Normal high
- Record high
- Record low
September at a glance
- Average high
- 80°F
- Average low
- 56°F
- Precipitation
- 4.05 in
- Record high
- 111°FSep 3, 1947
- Record low
- 27°FSep 28, 1908
- Chance of a freeze
- 6%
- Days of 90°F or more
- 4.6
- Daylight
- 13 h 01 min to 11 h 49 min
- Cloud cover
- 45%
- Humidity
- 69%
- Dew point
- 57°F
- Wind
- 9.6 mph
Every day of the month
A wet day has at least 0.01 inch of precipitation; snow means at least 0.1 inch of snowfall.
| Date | Normal high | Normal low | Record high | Record low | Chance wet | Chance of snow |
|---|---|---|---|---|---|---|
| Sep 1 | 85°F | 61°F | 107°F 2000 | 43°F 1903 | 28% | 0% |
| Sep 2 | 85°F | 61°F | 109°F 2000 | 44°F 1949 | 28% | 0% |
| Sep 3 | 84°F | 61°F | 111°F 1947 | 44°F 1974 | 28% | 0% |
| Sep 4 | 84°F | 60°F | 104°F 1947 | 43°F 1905 | 28% | 0% |
| Sep 5 | 84°F | 60°F | 107°F 1913 | 42°F 1974 | 28% | 0% |
| Sep 6 | 83°F | 60°F | 105°F 1936 | 43°F 1988 | 28% | 0% |
| Sep 7 | 83°F | 59°F | 109°F 1947 | 41°F 1898 | 28% | 0% |
| Sep 8 | 83°F | 59°F | 101°F 1922 | 40°F 1898 | 28% | 0% |
| Sep 9 | 83°F | 59°F | 101°F 2026 | 41°F 1943 | 28% | 0% |
| Sep 10 | 82°F | 58°F | 101°F 1936 | 41°F 1929 | 28% | 0% |
| Sep 11 | 82°F | 58°F | 103°F 2000 | 40°F 1940 | 28% | 0% |
| Sep 12 | 82°F | 58°F | 104°F 1956 | 36°F 1902 | 28% | 0% |
| Sep 13 | 81°F | 57°F | 100°F 1911 | 30°F 1902 | 28% | 0% |
| Sep 14 | 81°F | 57°F | 100°F 1939 | 37°F 2014 | 28% | 0% |
| Sep 15 | 81°F | 56°F | 100°F 1939 | 34°F 1904 | 28% | 0% |
| Sep 16 | 80°F | 56°F | 100°F 1931 | 40°F 1903 | 28% | 0% |
| Sep 17 | 80°F | 56°F | 100°F 1953 | 36°F 1903 | 28% | 0% |
| Sep 18 | 80°F | 55°F | 100°F 1931 | 33°F 1901 | 28% | 0% |
| Sep 19 | 79°F | 55°F | 102°F 1954 | 36°F 1991 | 28% | 0% |
| Sep 20 | 79°F | 54°F | 98°F 2022 | 34°F 1901 | 28% | 0% |
| Sep 21 | 79°F | 54°F | 98°F 1956 | 34°F 1983 | 28% | 0% |
| Sep 22 | 78°F | 54°F | 97°F 1937 | 32°F 1995 | 28% | 0% |
| Sep 23 | 78°F | 53°F | 97°F 1939 | 32°F 1983 | 28% | 0% |
| Sep 24 | 78°F | 53°F | 93°F 1984 | 30°F 1989 | 28% | 0% |
| Sep 25 | 77°F | 52°F | 93°F 1904 | 35°F 1989 | 28% | 0% |
| Sep 26 | 77°F | 52°F | 97°F 1953 | 31°F 1912 | 28% | 0% |
| Sep 27 | 77°F | 52°F | 96°F 1956 | 30°F 1942 | 28% | 0% |
| Sep 28 | 76°F | 51°F | 104°F 1953 | 27°F 1908 | 27% | 0% |
| Sep 29 | 76°F | 51°F | 101°F 1953 | 27°F 1908 | 27% | 0% |
| Sep 30 | 75°F | 50°F | 95°F 1938 | 28°F 1984 | 27% | 0% |
Chance of rain
- Chance of a wet day
- Chance of snowfall
Sunrise and sunset
Times for 2026, local time (CDT).
- September 1
- sunrise 6:50 AM, sunset 7:51 PM
- September 30
- sunrise 7:16 AM, sunset 7:05 PM
Other months
Sources
Normals: NOAA NCEI U.S. Climate Normals, 1991-2020, station USC00146128 (Ottawa), public domain. Records: NOAA GHCN-Daily, station USC00146128, every year on file, quality-flagged values removed. Cloud, humidity, wind and sunshine: 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.