Average monthly Rainfall, Sunshine, Temperatures. Graphical Climatology of Chicago Temperatures, Precipitation, and Snowfall (1871-Present) The following is a graphical climatology of Chicago, Illinois temperatures, precipitation, and snowfall, from the 1870’s at the earliest (temperature and precipitation) into 2020. Illinois Climate Normals Maps; Illinois Current Climate Conditions; Climate Graphs for Area Cities; Median Date of First Autumn Freeze (32F) Median Date of First Autumn Hard Freeze (28F) Median Date of Last Spring Freeze (32F) Median Date of Last Spring Hard Freeze (28F) Average Yearly Rainfall Maps. Illinois has been noted as a microcosm of the entire United States. Climate and average weather for Chicago (Illinois), United States of America displayed in graphs. Illinois (/ ˌ ɪ l ə ˈ n ɔɪ / IL-ə-NOY) is a state in the Midwestern and Great Lakes regions of the United States.It has the fifth largest gross domestic product (GDP), the sixth largest population, and the 25th largest land area of all U.S. states. Illinois normal annual precipitation map Climate Change in Illinois Dr. Jim Angel, State Climatologist. History of the Chicago and Rockford Weather Observation Sites; How to obtain OFFICIAL Climate Data; NOAA Climate Data; NCDC-National Climatic Data Center We know the climate in Illinois has changed in the past due to natural forces such as changes in the amount of solar radiation, ocean circulation, volcanoes, etc. Local Climate Studies. The climate of Chicago is classified as hot-summer humid continental (Köppen: Dfa), with all four seasons distinctly represented: Winters are cold and see frequent snow and near 0 °F (−18 °C) windchill temperatures, while summers are warm and humid with temperatures being hotter inland, spring and fall bring bouts of both cool and warm weather and fairly sunny skies. January February March April May June July August September October November December; Average Monthly high in °F: 31° 38° 50° 62° 73° 82° 86° 84° 78° 66° 50° Chicago, Illinois climate information including graphs for average temperature, annual rainfall Averages are for Chicago Midway Airport, which is 9 miles from Chicago. Climate data and weather averages in Chicago. Past Events and Scientific Studies; Climate Graphs. Holiday Statistics and Graphs for Chicago and Rockford; Climate Plots for Northern Illinois and Northwest Indiana; Other. Annual Weather Averages Near Chicago. Climate change has become a major issue will have direct and indirect impacts on Illinois. Find the best time to go to Chicago (Illinois).