Illinois weather by month

Check out Illinois weather averages by month. Compare detailed monthly climate statistics including temperature, rainfall and sunshine figures.

  Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Maximum daytime temperature °F
30°F maximum daytime temperature in January in Chicago30
34°F maximum daytime temperature in February in Chicago34
46°F maximum daytime temperature in March in Chicago46
59°F maximum daytime temperature in April in Chicago59
70°F maximum daytime temperature in May in Chicago70
81°F maximum daytime temperature in June in Chicago81
84°F maximum daytime temperature in July in Chicago84
82°F maximum daytime temperature in August in Chicago82
75°F maximum daytime temperature in September in Chicago75
63°F maximum daytime temperature in October in Chicago63
48°F maximum daytime temperature in November in Chicago48
36°F maximum daytime temperature in December in Chicago36
Hours of sunshine (daily)
Days with some rainfall
12 days with some rainfall in January in Chicago12
10 days with some rainfall in February in Chicago10
13 days with some rainfall in March in Chicago13
13 days with some rainfall in April in Chicago13
11 days with some rainfall in May in Chicago11
10 days with some rainfall in June in Chicago10
10 days with some rainfall in July in Chicago10
9 days with some rainfall in August in Chicago9
9 days with some rainfall in September in Chicago9
9 days with some rainfall in October in Chicago9
11 days with some rainfall in November in Chicago11
12 days with some rainfall in December in Chicago12
Sea temperature °F
39°F sea temperature in January in Chicago39
37°F sea temperature in February in Chicago37
37°F sea temperature in March in Chicago37
37°F sea temperature in April in Chicago37
43°F sea temperature in May in Chicago43
54°F sea temperature in June in Chicago54
66°F sea temperature in July in Chicago66
70°F sea temperature in August in Chicago70
66°F sea temperature in September in Chicago66
57°F sea temperature in October in Chicago57
48°F sea temperature in November in Chicago48
41°F sea temperature in December in Chicago41

More about Illinois

Illinois by month

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

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The climate guide for Illinois (Chicago) shows long term monthly weather averages processed from data supplied by CRU (University of East Anglia), the Met Office & the Netherlands Meteorological Institute. Find out more about our data sources.

Top Illinois destinations

Below are average maximum temperatures at popular countries, regions and places in Illinois for next month - May. Select a destination to see the climate guide for all months of the year.

All Illinois destinations

Metric (°C)  |  Imperial (°F)

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More about the USA

Compare Illinois with the UK

Below the Illinois chart shows average maximum daytime temperature for Illinois, USA (Chicago) and the UK (London).

Maximum daytime temperature (°F)

Illinois, USA (Chicago)
UK (London)
45
34
45
46
50
59
55
70
63
81
68
84
72
82
72
75
66
63
59
48
50
36
46
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
30

Metric (°C)  |  Imperial (°F)

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