Illinois Annual Rainfall and Climate Data, see below for individual cities 

 Illinois Average Annual Precipitation

Illinois city precipitation totals

City

Avg Annual Precip

Avg Annual Snow

Avg. days of Precip Avg # snow days Avg # thunderstorm days Avg # hail days Avg # severe thunderstorm watches per year Avg # tornado watches per year # of tornadoes reported in county, 1960-2010
Chicago 36.27 38.0 126 69 38 2 4 13 41
Moline 38.04 30.5 114 51 46 1 6 15 17
Peoria 36.03 25.0 114 50 30 2 7 15 20
Rockford 36.63 34.5 118 70 43 2 4 12 9
Springfield 35.56 23.1 114 50 50 1 7 14 69
  • Illinois Annual Precipitation Average - 39.32 inches, 37th wettest state in the U.S. 
  • Illinois Tornado Average - 25.8 per year - 9th most most in the U.S.
  • Largest reported Tornado in Illinois from 1950-2011, 7/23/1975 - 2,630 yards / 1.49 miles wide
  • Date with highest number of reported Tornadoes in Illinois from 1950-2011, April 19th - 68 tornadoes
  • Average time of occurrence of reported Tornadoes in Illinois from 1950-2011 - 4:06 pm 
  • Illinois Annual Lightning Density - 14.6 flashes per square mile - 9th highest in U.S. 
  • Record Driest year Illinois from 1895-2012 - 1901, avg precipitation 26.34 inches 
  • Record Wettest year in Illinois from 1895-2012 - 1993, avg precipitation 51.19 inches 

Illinois Precipitation Records

  • Driest location ranked by lowest annual average precipitation: Waukegan, northern Illinois, 32.32"
  • Wettest location ranked by highest annual average precipitation: Rosiclare, southern Illinois, 104.18"
  • Snowiest location ranked by highest annual average snowfall: Chicago Midway Airport, northern Illinois, 42.8"
  • State precipitation record for 24 hours - Aurora, northeastern Illinois, 7/17-18/1996, 16.94"
  • State precipitation record for 1 year - New Burnside, southern Illinois, 1950, 74.58"
  • State snowfall record for 24 hours - Astoria, western Illinois, 7/17-18/1996, 16.94"
  • State snow record for 1 season - Antioch, northeastern Illinois, 1978-1979, 103.3"
  • On 01/31/1982, a major snowstorm struck Illinois. Twenty-five inches of snow was recorded at Greenville, Illinois
    located east of Saint Louis. The storm left 4,000 motorists stranded for two days
  • Winter snowfall is heaviest in the Chicago area, enhanced by lake-effect snows from Lake Michigan.
  • The number of annual days in Illinois with an inch or more of precipitation averages 11 days and the number of days
    with an inch or more of snow averages 8 days
  • On April 2, 1975 the biggest snowstorm of record for so late in the season paralyzed Chicago, IL. Up to 20 inches of
    snow fell in extreme northeastern Illinois, and 10.9 inches of snow closed Chicago's O'Hare Airport.
  • Flood losses in Illinois - $257 million annually since 1983 - are the third highest in the nationIllinois temperature
    averages and extremes, Chicago climate records, precipitation and temperature data for all U.S. states and
    interesting Top 10 U.S. climate extremes
Data sources: National Climatic Data Center, Severe thunderstorm / tornado watch data period is 1999 - 2008, NOAA Storm Prediction Center, Tornado climate data - NOAA Storm Prediction Center
State lightning flash density average - 1997-2011, Vaisala
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