Hot, Humid Weather in Illinois





The information here tells how often heat combines with humidity in Illinois cities to create uncomfortably muggy weather.

The apparent temperature, also known as the Heat Index, measures how hot the weather really feels, considering both temperature and humidity. For instance, a temperature of 90 degrees Fahrenheit (32.2 ° Celsius) along with 60 % humidity pushes the apparent temperature to 100 °F (37.8 °C).

These tables list the number of days when the actual temperature and the apparent temperature rose to least 95, 105 or 115 °F (35, 40.6 or 46.1 °C) for an hour or more. The totals are for the 30 years from 1978 to 2007.

The final table breaks the totals into yearly averages for the days when apparent temperatures reach 95 and 105 °F.

Total days with the temperature at least 95 °F
City Actual Apparent
Chicago 93 375
Moline 154 592
Peoria 117 592
Quincy 174 658
Rockford 76 351
Springfield 130 707
Total days with the temperature at least 105 °F
City Actual Apparent
Chicago 0 60
Moline 0 116
Peoria 0 123
Quincy 2 123
Rockford 0 54
Springfield 0 145
Total days with the temperature at least 115 °F
City Actual Apparent
Chicago 0 3
Moline 0 5
Peoria 0 6
Quincy 0 9
Rockford 0 3
Springfield 0 12
Average days a year of apparent temperature
City 95+ °F 105+ °F
Chicago 13 2
Moline 20 4
Peoria 20 4
Quincy 22 4
Rockford 12 2
Springfield 24 5
References

Peter Browning and Brian Walawender. 2009. A Climatology of Apparent Temperature. 21st Conference on Climate Variability and Change.

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