McHenry County Weather in September
Average highs run from 79°F on September 1 to 66°F on September 30, and lows from 48°F to 37°F. Normal precipitation for the month is 1.56 in over about 4 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
- 73°F
- Average low
- 43°F
- Precipitation
- 1.56 in
- Snowfall
- 0.1 in
- Record high
- 106°FSep 4, 1978
- Record low
- 21°FSep 26, 1965
- Chance of a freeze
- 82%
- Days of 90°F or more
- 1.1
- Daylight
- 13 h 24 min to 11 h 42 min
- Cloud cover
- 56%
- Humidity
- 60%
- Dew point
- 43°F
- Wind
- 11.0 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 | 79°F | 48°F | 99°F 2022 | 36°F 1974 | 16% | 0% |
| Sep 2 | 78°F | 48°F | 98°F 1960 | 35°F 1974 | 16% | 0% |
| Sep 3 | 78°F | 48°F | 100°F 1978 | 35°F 1961 | 16% | 0% |
| Sep 4 | 78°F | 47°F | 106°F 1978 | 36°F 1958 | 15% | 0% |
| Sep 5 | 77°F | 47°F | 104°F 2001 | 33°F 1956 | 15% | 0% |
| Sep 6 | 77°F | 47°F | 101°F 1976 | 29°F 1956 | 15% | 0% |
| Sep 7 | 76°F | 46°F | 97°F 2003 | 34°F 2020 | 15% | 0% |
| Sep 8 | 76°F | 46°F | 95°F 1994 | 32°F 2020 | 15% | 0% |
| Sep 9 | 76°F | 45°F | 99°F 1994 | 33°F 2006 | 15% | 0% |
| Sep 10 | 75°F | 45°F | 96°F 1981 | 30°F 1955 | 15% | 0% |
| Sep 11 | 75°F | 45°F | 94°F 1948 | 25°F 1955 | 15% | 0% |
| Sep 12 | 74°F | 44°F | 98°F 2017 | 31°F 1970 | 15% | 0% |
| Sep 13 | 74°F | 44°F | 91°F 1959 | 28°F 1970 | 15% | 0% |
| Sep 14 | 73°F | 44°F | 88°F 1968 | 25°F 1964 | 15% | 1% |
| Sep 15 | 73°F | 43°F | 97°F 1948 | 25°F 1959 | 15% | 1% |
| Sep 16 | 73°F | 43°F | 95°F 1979 | 24°F 1959 | 15% | 1% |
| Sep 17 | 72°F | 42°F | 94°F 1989 | 22°F 1959 | 15% | 1% |
| Sep 18 | 72°F | 42°F | 92°F 2004 | 31°F 1991 | 14% | 1% |
| Sep 19 | 71°F | 41°F | 90°F 1960 | 27°F 1957 | 14% | 1% |
| Sep 20 | 71°F | 41°F | 94°F 1960 | 30°F 1995 | 14% | 1% |
| Sep 21 | 70°F | 41°F | 84°F 2008 | 25°F 1995 | 14% | 1% |
| Sep 22 | 70°F | 40°F | 88°F 2020 | 26°F 2012 | 14% | 1% |
| Sep 23 | 69°F | 40°F | 87°F 1992 | 28°F 1951 | 14% | 1% |
| Sep 24 | 69°F | 39°F | 90°F 1992 | 27°F 1951 | 13% | 1% |
| Sep 25 | 68°F | 39°F | 93°F 2014 | 26°F 1965 | 13% | 1% |
| Sep 26 | 68°F | 38°F | 92°F 2014 | 21°F 1965 | 13% | 1% |
| Sep 27 | 67°F | 38°F | 93°F 2021 | 28°F 1961 | 13% | 1% |
| Sep 28 | 67°F | 37°F | 96°F 2021 | 26°F 1951 | 13% | 1% |
| Sep 29 | 66°F | 37°F | 97°F 2024 | 27°F 1974 | 12% | 1% |
| Sep 30 | 66°F | 37°F | 93°F 1989 | 22°F 1974 | 12% | 1% |
Chance of rain
- Chance of a wet day
- Chance of snowfall
Sunrise and sunset
Times for 2026, local time (CDT).
- September 1
- sunrise 7:00 AM, sunset 8:24 PM
- September 30
- sunrise 7:41 AM, sunset 7:23 PM
Other months
Sources
Normals: NOAA NCEI U.S. Climate Normals, 1991-2020, station USC00328792 (Towner 2 Ne), public domain. Records: NOAA GHCN-Daily, station USW00024013, 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 2026-09-25. Sun and moon: computed with the NOAA solar equations and Meeus.