Illinois annual temperatures and extremes

Hottest temperature ever recorded: 117 F, E. St Louis, southwest Illinois, 7/14/1954

Coldest temperature ever recorded: -36 F, Congerville. central Illinois, 1/5/1999

Hottest location ranked by highest average annual temperature: Cairo, southern Illinois, 58.7 F

Coldest location ranked by lowest average annual temperature: Elizabeth, northwest Illinois, 46.9 F

On January 10, 1982, The temperature at O'Hare Airport in Chicago, IL, plunged to 26 degrees below 
zero, and high winds drove the wind chill reading to 77 degrees below zero. The temperature in Downtown
Chicago reached 23 degrees below zero. A week later a second arctic surge sent the temperature plunging 
back down to 25 degrees below zero.

During March 2007, Illinois temperatures were 47.5°F, or 6.4°F above normal and the sixth warmest March
since statewide records began in 1895. Just days later, a major cold front stormed through the state. The coldest
period was from April 4-9, with temperatures averaging 14.0°F below normal and the second coldest
April 4-9 period since 1900. The lowest daily low temperatures for this period averaged 20.9°F statewide. The 
surprising freeze caused millions of dollars in damage to agricultural crops.

During 1976-1977, a climatic rarity occurred in Chicago. October-January was the coldest such period on record,
and February-May was the hottest on record.

The largest 24 temperature drop in Chicago history occurred on November 11-12, 1911. A daily record high of 
74 degrees occurred at 4:00pm on November, 11. The temperature then plunged to 13 degrees by 12:30pm the 
following day, an amazing drop of 61 degrees in just 20 hours.

Northern Illinois averages 10 days at or above 90° F compared to over 40 days across southern parts of the State. Days at or above 100° F are infrequent, occurring about every other year in the north and two days annually in the south. Northern Illinois averages 140 days at or below 32° F in contrast to 80 such days the southern portion of the State. Days at or below 0° F decrease from 16 days annually (north) to two days (south).

Heat and cold waves are climate hazards associated with high death tolls. Illinois experienced two of its most deadly heat waves during the 1990s. The 1995 heat wave, the deadliest on record, led to 753 Illinois deaths. That heat wave and another one in 1999 caused major power outages in the Chicago metropolitan area. Annually, 74 deaths are attributed to heat, and 18 deaths are attributed to cold, far exceeding deaths due to tornadoes, lightning and floods.

City	Avg High Temp	Avg Low Temp	Avg Annual Temp	Avg # days > 90F	Avg # days < 32F	Record High Temp	Record Low Temp
Chicago	58.7	40.0	49.4	17	129	104 / 1988	-27 / 1985
Moline	60.1	39.9	50.0	23	134	104 / 1988	-28 / 1996
Peoria	60.8	41.3	51.0	22	126	105 / 1988	-25 / 1977
Rockford	58.1	38.2	48.1	15	144	104 / 1988	-27 / 1982
Springfield	62.7	42.8	52.8	29	116	112 / 1954	-22 / 1963
Illinois annual average temperature - 51.74 degrees, 23rd warmest state in the U.S. Record Hottest year in Illinois - 1921 / Avg temperature 55.61 degrees Record Coldest year in Illinois - 1917 / Avg temperature 48.67 degrees Illinois average Summer temperature (June, July, August) - 73.4 F degrees, 17th warmest U.S. summer state Illinois average Winter temperature (December, January, February) - 28.3 F degrees, 19th coldest U.S. winter state