Illinois: Temperature Extremes
Updated February 21, 2017 | Factmonster Staff 
| Month | Maximum °F | Year | Place | Minimum °F | Year | Place |
|---|---|---|---|---|---|---|
| Jan. | 78 | 1986 | Cahokia | –36 | 1999 | Congerville |
| Feb. | 83 | 2000 | Kaskaskia River* | –35 | 1996 | Elizabeth |
| March | 94 | 1929 | Harrisburg | –21 | 1962 | Freeport |
| April | 99 | 1989 | Kaskaskia | –2 | 1982 | Mount Carroll |
| May | 107 | 1934 | Sycamore* | 21 | 1989 | Elizabeth |
| June | 108 | 1954 | Palestine | 29 | 1972 | Marengo |
| July | 117 | 1954 | East St. Louis | 35 | 1904 | Lanark |
| Aug. | 113 | 1934 | La Harpe | 31 | 1915 | La Grange |
| Sept. | 109 | 1925 | Harrisburg | 14 | 1899 | Lanarck* |
| Oct. | 98 | 1953 | Harrisburg* | 1 | 1925 | La Harpe |
| Nov. | 89 | 1987 | Waterloo | –20 | 1947 | Rockford |
| Dec. | 79 | 1982 | Cairo | –29 | 2000 | Elizabeth* |
*Also on earlier dates at the same time or other places.
