Cook County Weather in September
Average highs run from 88°F on September 1 to 83°F on September 30, and lows from 70°F to 63°F. Normal precipitation for the month is 4.42 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
- 86°F
- Average low
- 67°F
- Precipitation
- 4.42 in
- Record high
- 101°FSep 8, 1990
- Record low
- 46°FSep 30, 1967
- Chance of a freeze
- 0%
- Days of 90°F or more
- 10.7
- Daylight
- 12 h 47 min to 11 h 53 min
- Cloud cover
- 49%
- Humidity
- 77%
- Dew point
- 68°F
- Wind
- 6.7 mph
Every day of the month
A wet day has at least 0.01 inch of precipitation.
| Date | Normal high | Normal low | Record high | Record low | Chance wet |
|---|---|---|---|---|---|
| Sep 1 | 88°F | 70°F | 100°F 1951 | 62°F 1999 | 30% |
| Sep 2 | 88°F | 70°F | 98°F 2024 | 58°F 1999 | 29% |
| Sep 3 | 88°F | 70°F | 97°F 1951 | 62°F 1968 | 29% |
| Sep 4 | 87°F | 70°F | 99°F 1951 | 63°F 2025 | 29% |
| Sep 5 | 87°F | 69°F | 99°F 2013 | 61°F 1994 | 28% |
| Sep 6 | 87°F | 69°F | 96°F 1954 | 59°F 1997 | 28% |
| Sep 7 | 87°F | 69°F | 98°F 1990 | 59°F 2011 | 28% |
| Sep 8 | 87°F | 69°F | 101°F 1990 | 55°F 2011 | 27% |
| Sep 9 | 87°F | 69°F | 98°F 1954 | 56°F 2011 | 27% |
| Sep 10 | 87°F | 68°F | 98°F 1954 | 59°F 2011 | 27% |
| Sep 11 | 87°F | 68°F | 98°F 1954 | 59°F 1969 | 27% |
| Sep 12 | 86°F | 68°F | 99°F 1954 | 58°F 2003 | 26% |
| Sep 13 | 86°F | 68°F | 97°F 1991 | 58°F 2015 | 26% |
| Sep 14 | 86°F | 68°F | 98°F 1991 | 55°F 2015 | 26% |
| Sep 15 | 86°F | 67°F | 98°F 2011 | 56°F 2025 | 26% |
| Sep 16 | 86°F | 67°F | 99°F 1990 | 52°F 1976 | 26% |
| Sep 17 | 86°F | 67°F | 98°F 2019 | 55°F 2001 | 26% |
| Sep 18 | 85°F | 67°F | 98°F 2005 | 56°F 1981 | 26% |
| Sep 19 | 85°F | 66°F | 96°F 1954 | 47°F 1981 | 25% |
| Sep 20 | 85°F | 66°F | 97°F 1990 | 47°F 1981 | 25% |
| Sep 21 | 85°F | 66°F | 99°F 1997 | 50°F 1981 | 25% |
| Sep 22 | 85°F | 66°F | 97°F 1990 | 52°F 1983 | 25% |
| Sep 23 | 84°F | 65°F | 95°F 1992 | 50°F 1982 | 25% |
| Sep 24 | 84°F | 65°F | 97°F 2019 | 51°F 1987 | 25% |
| Sep 25 | 84°F | 65°F | 100°F 2019 | 49°F 1990 | 25% |
| Sep 26 | 84°F | 65°F | 98°F 2019 | 50°F 2001 | 24% |
| Sep 27 | 84°F | 64°F | 98°F 2019 | 51°F 2001 | 24% |
| Sep 28 | 83°F | 64°F | 96°F 1986 | 52°F 1983 | 24% |
| Sep 29 | 83°F | 64°F | 93°F 1986 | 47°F 1967 | 24% |
| Sep 30 | 83°F | 63°F | 98°F 1990 | 46°F 1967 | 24% |
Chance of rain
- Chance of a wet day
Sunrise and sunset
Times for 2026, local time (EDT).
- September 1
- sunrise 7:10 AM, sunset 7:57 PM
- September 30
- sunrise 7:27 AM, sunset 7:20 PM
Other months
Sources
Normals: NOAA NCEI U.S. Climate Normals, 1991-2020, station USC00096087 (Moultrie 2 Ese), public domain. Records: NOAA GHCN-Daily, station USW00093845, 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.