CHICAGO O'HARE INTERNATIONAL climate by month
Averages and records for each calendar month at CHICAGO O'HARE INTERNATIONAL, United States, from 1958 to 2026. The warmest month is July, averaging 28.9°C; the coolest is January at −1.0°C.
| Month | Avg high | Avg low | Record high | Record low | Years |
|---|---|---|---|---|---|
| January | −1.0°C | −9.2°C | 18.3°C31 January 1989 | −32.8°C20 January 1985 | 68 / 68 |
| February | 1.5°C | −7.2°C | 23.3°C27 February 2024 | −28.3°C3 February 1996 | 68 / 68 |
| March | 8.0°C | −1.6°C | 31.1°C29 March 1986 | −22.2°C1 March 1962 | 68 / 68 |
| April | 14.9°C | 3.9°C | 32.8°C22 April 1980 | −13.9°C7 April 1982 | 68 / 68 |
| May | 21.2°C | 9.4°C | 36.1°C27 May 2012 | −4.4°C10 May 1966 | 68 / 68 |
| June | 26.7°C | 14.8°C | 40.0°C20 June 1988 | 2.2°C22 June 1963 | 68 / 68 |
| July | 28.9°C | 17.8°C | 40.0°C13 July 1995 | 4.4°C1 July 1965 | 68 / 68 |
| August | 27.9°C | 17.2°C | 38.3°C2 August 1991 | 5.0°C15 August 1964 | 68 / 68 |
| September | 24.1°C | 12.9°C | 37.2°C7 September 1960 | −2.2°C23 September 1974 | 67 / 68 |
| October | 17.2°C | 6.4°C | 32.8°C6 October 1963 | −8.3°C24 October 1981 | 67 / 67 |
| November | 9.1°C | 0.2°C | 25.6°C5 November 1978 | −17.2°C30 November 1958 | 68 / 68 |
| December | 2.0°C | −5.9°C | 21.7°C2 December 1982 | −31.7°C24 December 1983 | 68 / 68 |
Years shows the number behind the average high, then the number holding a record for that month. They differ because a year contributes an average only when the month has at least 25 days of readings, while a single reading is enough to set a record. The average low is withheld on the same 25-day rule and is counted separately again; it is shown as a dash where the archive cannot support it. Across the twelve months here the averages rest on 67 to 68 years each.
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Every figure on this page is computed from NOAA GHCN-Daily observations stored per station, per year, per month. Nothing is modelled, interpolated or estimated, and a month the archive never covered is left out rather than filled in. A station appears here only once all twelve months carry an average from at least 10 years. See how this is built.