High Temperatures
On April 21 in Chicago, IL (Illinois), USA, the average high temperature is 61.7 °F (16.5 °C). The lowest recored high temperature was 42.1 °F (5.6 °C) in 2021 and the highest recored high temperature was 89.1 °F (31.7 °C) in 1987. The high temperature is usually* between 54.3 °F (12.4 °C) and 69.1 °F (20.6 °C). About a quarter of the time, the high temperature is less than 54.3 °F (12.4 °C), and another quarter of the time, the high temperature is greater than and 69.1 °F (20.6 °C). About 95% of the time, the high temperature has been between 40.3 °F (4.6 °C) and 83.1 °F (28.4 °C).
Low Temperatures
On April 21 in Chicago, IL (Illinois), USA, the average low temperature is 43.2 °F (6.2 °C). The lowest recored low temperature was 25.2 °F (-3.8 °C) in 1982 and the lowest recored low temperature was 70.0 °F (21.1 °C) in 1985. The low temperature is usually* between 37.8 °F (3.2 °C) and 48.5 °F (9.2 °C). About a quarter of the time, the low temperature is less than 37.8 °F (3.2 °C), and another quarter of the time, the low temperature is greater than and 48.5 °F (9.2 °C). About 95% of the time, the low temperature has been between 27.7 °F (-2.4 °C) and 58.7 °F (14.8 °C).
Frost
On April 21 in Chicago, IL (Illinois), USA, expect the temperatures to drop below freezing for a risk of frost about 7.9% of the time.
Data Source(s)
The data used to compute the average high/low temperatures for this location were taken from the following stations:
- 9087044 - CALUMET IL — Integrated Surface Dataset (ISD) station ID: 997255 — from year 2005 to 2025
- NORTHERLY ISLAND — Integrated Surface Dataset (ISD) station ID: 998499 — from year 2013 to 2025
- CHICAGO — Integrated Surface Dataset (ISD) station ID: 997338 — from year 2005 to 2025
- CHICAGO MIDWAY INTL ARPT — Integrated Surface Dataset (ISD) station ID: 725340 — Weather Bureau Army Navy (WBAN): 14819 — from year 1973 to 2025
- CHICAGO O'HARE INTERNATIONAL — Integrated Surface Dataset (ISD) station ID: 725300 — Weather Bureau Army Navy (WBAN): 94846 — from year 1947 to 2025
- FOSTER AVE CHICAGO — Integrated Surface Dataset (ISD) station ID: 998497 — from year 2015 to 2019
- CHICAGO/MEIGS — Integrated Surface Dataset (ISD) station ID: 725346 — from year 2000 to 2002
- CHICAGO/MEIGS — Integrated Surface Dataset (ISD) station ID: 725346 — Weather Bureau Army Navy (WBAN): 94866 — from year 1973 to 1999
- CHICAGO / CALUMET COAST GUARD — Integrated Surface Dataset (ISD) station ID: 725344 — from year 1994 to 1996
- NAVAL AIR STATION — Integrated Surface Dataset (ISD) station ID: 725306 — Weather Bureau Army Navy (WBAN): 14855 — from year 1973 to 1994
- WILMETTE (MARINES)& — Integrated Surface Dataset (ISD) station ID: 725307 — from year 1976 to 1994
- WILMETTE (CGS) — Integrated Surface Dataset (ISD) station ID: 722417 — from year 1988 to 1990
- CALUMET (CGS) — Integrated Surface Dataset (ISD) station ID: 722418 — from year 1989 to 1989
- CHICAGO OHARE INTL AP — Weather Bureau Army Navy (WBAN): 94846 — from year 1970 to 1972
- NAVAL AIR STATION — Weather Bureau Army Navy (WBAN): 14855 — from year 1945 to 1972
- CHICAGO MIDWAY AP — Weather Bureau Army Navy (WBAN): 14819 — from year 1948 to 1972
- CHICAGO MEIGS FIELD — Weather Bureau Army Navy (WBAN): 94866 — from year 1966 to 1970
- PARK RIDGE AF — Weather Bureau Army Navy (WBAN): 14810 — from year 1949 to 1958
- DUNNE CRIB IL. — Integrated Surface Dataset (ISD) station ID: 744650 — from year 1944 to 1944