The spring Chicago, Illinois weather season features normal temperatures from near 40/20°F (Hi/Lo) in early March to the middle 70s/low 50s towards the end of May. Nearly 10 inches of liquid precipitation can be expected for the 3 month period. Normal snowfall for the first part of the spring period is approximately 7 1/2 inches. On average, the last flurries fall by mid April. Chicago temperature records indicate that the average last spring freeze typically occurs by late April. On May 25th, 1992, Chicago O’Hare Airport (official observation site) recorded a 32°F reading… the latest freeze on record. On a much warmer note, the earliest seasonal 80°F/plus reading ever at O’Hare occured on March 11th, 1990 when the mercury hit 81°F – a benchmark typically reached in late April.
Meteorological Summer ( June 1st – August 31st )
The summer weather season features normal Chicago temperatures from the middle to upper 70s/mid 50s in early June to the lower and mid 80s/low 60s by mid July. Just over 11 inches of rain can be expected for the three month period. In August of 1987, the monthly total exceeded that figure. As far as summer temperature averages go, typically Chicago O’Hare Airport logs 17 90s during the entire warm season. In 1988, O’Hare Field logged 47 90°F/plus days which included 7 100s – a record intact. In stark contrast, 2004 has taken on new meaning for summer Chicago record temperatures. The city recorded it’s 15th coolest summer since 1871 – appx. 3° below normal. August was the coolest of the period with only 10 days at or above 80° and 3 record lows in the upper 40s.
Meteorological Fall ( September 1st – November 30th )
The fall or autumn season features normal Hi/Lo temperatures from the upper 70s/mid 50s in early September to around 40/20°F for extremes by the tail end of November. Approximately 9 inches of liquid precip can be expected for the 3 month period. Normal snowfall for the second half of the period is close to 2 inches. On average, the first flurries begin to fly by the very end of October. The average first freeze typically occurs by early October in the suburbs and early November Downtown. In 1995, Chicago OHare saw a freeze on September 22nd, the earliest ever. On the flipside, fall Chicago weather records prove that warmth can have staying power. In Nov. 1999, O’Hare Apt. recorded 5 70°/plus days through the 18th. The average last 70 usually occurs by November 1st.
Meteorological Winter ( December 1st – February 28th )
Winter translates into average Chicago temperature extremes around 30/15°F for the entire month of January. Nearly 6″ of liquid precip, including 30″ of snowfall is normal for the 3 month period. The entire snow season can typically see 40″. On January 2nd, 1999, O’Hare logged 18.6″, making it Chicago’s greatest daily snowfall on record. The greatest snowfall total for an entire snow season goes to 1978-79 with an official 74.5″. As for winter’s chill.. the coldest temp ever recorded at Chicago O’Hare was -27°F in January of 1985. Warmest Chicago winter temperatures can be equally dramatic. On Dec. 2nd, 1982 O’Hare Airport’s daily extremes were 71°/58°. The day’s minimum or low was 20° warmer than the normal Hi. Incidently, 4.47″ of rain fell that same day.