Illinois · county records since 1895, through September 2026.
Weather › Illinois › Williamson County
Williamson County just had its warmest September ever recorded, +8° against the usual. The last 12 months brought 33.1 inches of rain and snow there, 68% of the usual 48.3.
That is the 1991 to 2020 average for these dates in Williamson County. The Weather Service forecast fills in below.
Loading the forecast...
Each bar is a month's average temperature against the usual for that month (1991 to 2020). Ranks compare the same month in every year since 1895.
Rain and melted snow against the usual for each month. The drought reading is NOAA's Palmer index for the county.
| Month | Usual high / low | Usual rain | Warmest | Coldest |
|---|---|---|---|---|
| January | 41° / 25° | 3.4 in | 42.4° 2006 | 15.1° 1977 |
| February | 46° / 28° | 3.2 in | 45.9° 2017 | 21.5° 1899 |
| March | 56° / 36° | 4.5 in | 59.6° 2012 | 30.6° 1960 |
| April | 68° / 45° | 5.5 in | 63.6° 2026 | 47.4° 1907 |
| May | 77° / 55° | 5.1 in | 72.4° 2018 | 58.8° 1917 |
| June | 85° / 64° | 4.5 in | 80.2° 1952 | 68.0° 1903 |
| July | 88° / 68° | 4.0 in | 84.1° 2012 | 71.9° 2014 |
| August | 87° / 65° | 3.3 in | 83.4° 1936 | 69.9° 1915 |
| September | 81° / 57° | 3.4 in | 76.8° 2026 | 61.4° 1918 |
| October | 70° / 46° | 3.7 in | 64.3° 1963 | 50.6° 1917 |
| November | 56° / 36° | 4.2 in | 54.5° 1909 | 36.8° 1976 |
| December | 45° / 28° | 3.6 in | 46.8° 2021 | 22.7° 1989 |
Warmest and coldest are the month's whole-month average temperature, with the year it happened.
Crime Radar: Marion, Herrin, Carterville