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Climate in Illinois

Illinois, Illinois gets 40 inches of rain, on average, per year. The US average is 38 inches of rain per year.

Illinois averages 22 inches of snow per year. The US average is 28 inches of snow per year.

On average, there are 198 sunny days per year in Illinois. The US average is 205 sunny days.

Illinois gets some kind of precipitation, on average, 108 days per year. Precipitation is rain, snow, sleet, or hail that falls to the ground. In order for precipitation to be counted you have to get at least .01 inches on the ground to measure.

Weather Highs & Lows

Summer High: the July high is around 86 degrees
Winter Low: the January low is 17

Illinois ranks 41/100 for Comfort Index

A higher score indicates a more comfortable year-round climate. The US average for the comfort index is 54. Our index is based on the total number of days annually within the comfort range of 70-80 degrees, and we also applied a penalty for days of excessive humidity.


Many people confuse weather and climate but they are different. Weather is the conditions of the atmosphere over a short period of time, and climate is how the atmosphere is over long periods of time.

Weather is how the atmosphere is behaving and its effects upon life and human activities. Weather can change from minute-to-minute. Most people think of weather in terms of temperature, humidity, precipitation, cloudiness, brightness, visibility, wind, and atmospheric pressure.

Climate is the description of the long-term pattern of weather in a place. Climate can mean the average weather for a particular region and time period taken over 30 years. Climate is the average of weather over time.


Climate Averages
  Illinois, IllinoisUnited States
  39.8 in.38.1 in.
  21.8 in.27.8 in.
  108.2 days106.2 days
  198 days205 days
  604 ft.2443 ft.

July is the hottest month for Illinois with an average high temperature of 85.6°, which ranks it as about average compared to other states. In Illinois, there are 4 comfortable months with high temperatures in the range of 70-85°. The most pleasant months of the year for Illinois are September, June and May.

January has the coldest nighttime temperatures for Illinois with an average of 17.4°. This is colder than most of the U.S. states.

Illinois has 20.5 days annually when the high temperature is over 90°, which is about average compared to other states in the U.S.

Illinois has 118.3 days annually when the nighttime low temperature falls below freezing, which is about average compared to other states in the U.S.

Illinois averages 6.6 days annually when the nighttime low temperature falls below freezing, which is colder than most states in the U.S.

May is the wettest month in Illinois with 4.5 inches of rain, and the driest month is January with 2.0 inches. The wettest season is Autumn with 30% of yearly precipitation and 17% occurs in Spring, which is the driest season.

Illinois's average annual rainfall of 39.8 inches indicates that it is about average compared to other states in the United States.

With an average annual snowfall of 21.8 inches, Illinois is less snowy than most states in the United States.

January is the snowiest month in Illinois with 6.8 inches of snow, and 5 months of the year have significant snowfall.

  • Annual Rainfall (US Avg: 36.5")
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    Reviews for Illinois    72 Reviews
    Peotone Ill - 8/21/2015
    I have been in the town of peotone for 13 years and now selling! I have never seen a more poor excuse for a town. There is no were to go and nothing too do. The town... Read More

    Start Your Review of Illinois

    36 years here - 8/1/2015
    I'm tired of everyone thinking chicago is all illinois is.... Even the politicians think only of Chicago... We have not had a state budget set yet amd people in small... Read More

    cost of living - 7/16/2015
    Illinois have one of the highest taxes in the... Read More

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