Illinois Climate

How Illinois's latest month ranks since 1895, the normals at its main weather stations, and the climate page for every town.

How Illinois is running

NOAA NCEI Climate at a Glance, from the nClimGrid analysis of every station, updated early each month. A rank of 1 is the highest or lowest of all years since 1895.

August 2026 in Illinois: 74.4°F (+0.8 °F against 1991-2020), the 41st warmest in 132 years on record.

August 2026 in Illinois: 5.34 in (+1.78 in against 1991-2020), the 9th wettest in 132 years on record.

January to August 2026 in Illinois: 56.5°F (+2.0 °F against 1991-2020), the 8th warmest in 132 years on record.

January to August 2026 in Illinois: 30.71 in (+2.08 in against 1991-2020), the 26th wettest in 132 years on record.

Warmest August: 80.8°F in 1947
Coolest August: 66.9°F in 1915
Wettest August: 6.86 in in 1977
Driest August: 1.16 in in 1897

Every year since 1895

Main weather stations

Annual 1991-2020 normals at the first-order (airport and Weather Service) stations; freeze dates are the median for 32°F.

Station	Avg high	Avg low	Precipitation	Snowfall	Last freeze	First freeze
Belleville Siu Rsch	68.9°F	46.4°F	43.36 in	11.2 in	April 12	October 20
Cahokia St Louis AP	66.5°F	46.4°F	40.84 in		April 8	October 26
Cairo 3N	68.2°F	48.0°F	51.00 in		April 2	October 31
Carbondale Southern Il AP	67.1°F	45.8°F	44.01 in		April 9	October 22
Champaign 9 Sw	61.4°F	40.8°F	39.62 in		April 23	October 13
Champaign Willard AP	62.8°F	42.1°F	36.97 in		April 19	October 17
Chicago Aurora Muni AP	59.7°F	39.1°F	33.84 in		April 28	October 13
Chicago Midway AP	60.2°F	44.0°F	34.42 in		April 11	October 31
Chicago Ohare Intl AP	59.5°F	43.0°F	37.86 in	38.4 in	April 16	October 28
Chicago Palwaukee AP	59.2°F	42.3°F	32.28 in		April 19	October 26
Chicago Waukegan Rgnl AP	57.2°F	39.3°F	35.30 in		April 30	October 21
Decatur AP	62.8°F	43.4°F	36.36 in		April 16	October 22
Lawrenceville Intl AP	65.9°F	45.5°F	41.66 in		April 8	October 26
Mattoon Coles CO AP	62.8°F	44.0°F	36.00 in		April 15	October 24
Moline Quad City Intl AP	61.5°F	40.9°F	38.27 in	36.1 in	April 24	October 18
Peoria Gtr Peoria AP	62.4°F	43.0°F	37.55 in	26.2 in	April 16	October 23
Quincy Rgnl AP	62.5°F	43.6°F	36.43 in		April 14	October 23
Rantoul	63.6°F	41.1°F	40.35 in		April 21	October 18
Rockford Gtr Rockford AP	58.8°F	40.0°F	37.24 in	37.1 in	April 24	October 17
Shabbona 5 Nne	57.7°F	37.9°F	37.41 in		April 28	October 10
Springfield Capital AP	64.1°F	44.0°F	38.04 in	21.8 in	April 14	October 20
West Chicago Dupage AP	59.2°F	40.2°F	33.23 in		April 25	October 19

Frost dates at every station in Illinois

Counties

Towns

Sources

Rankings: NOAA NCEI Climate at a Glance. Normals: NOAA NCEI U.S. Climate Normals, 1991-2020. Both public domain.