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

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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 - February. 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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Illinois weather averages

Temperature in Illinois (°F)

  Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Max temperature (daytime)
30°F maximum daytime temperature in January in Illinois (Chicago)30
34°F maximum daytime temperature in February in Illinois (Chicago)34
46°F maximum daytime temperature in March in Illinois (Chicago)46
59°F maximum daytime temperature in April in Illinois (Chicago)59
70°F maximum daytime temperature in May in Illinois (Chicago)70
81°F maximum daytime temperature in June in Illinois (Chicago)81
84°F maximum daytime temperature in July in Illinois (Chicago)84
82°F maximum daytime temperature in August in Illinois (Chicago)82
75°F maximum daytime temperature in September in Illinois (Chicago)75
63°F maximum daytime temperature in October in Illinois (Chicago)63
48°F maximum daytime temperature in November in Illinois (Chicago)48
36°F maximum daytime temperature in December in Illinois (Chicago)36
Min temperature (night-time)
14°F minimum night-time temperature in January in Illinois (Chicago)14
18°F minimum night-time temperature in February in Illinois (Chicago)18
28°F minimum night-time temperature in March in Illinois (Chicago)28
37°F minimum night-time temperature in April in Illinois (Chicago)37
48°F minimum night-time temperature in May in Illinois (Chicago)48
57°F minimum night-time temperature in June in Illinois (Chicago)57
63°F minimum night-time temperature in July in Illinois (Chicago)63
61°F minimum night-time temperature in August in Illinois (Chicago)61
54°F minimum night-time temperature in September in Illinois (Chicago)54
43°F minimum night-time temperature in October in Illinois (Chicago)43
32°F minimum night-time temperature in November in Illinois (Chicago)32
19°F minimum night-time temperature in December in Illinois (Chicago)19
Heat & Humidity
No heat & humidity in January in Illinois (Chicago)0
No heat & humidity in February in Illinois (Chicago)0
No heat & humidity in March in Illinois (Chicago)0
No heat & humidity in April in Illinois (Chicago)0
No heat & humidity in May in Illinois (Chicago)0
Low heat & humidity in June in Illinois (Chicago)L
Moderate heat & humidity in July in Illinois (Chicago)M
Moderate heat & humidity in August in Illinois (Chicago)M
No heat & humidity in September in Illinois (Chicago)0
No heat & humidity in October in Illinois (Chicago)0
No heat & humidity in November in Illinois (Chicago)0
No heat & humidity in December in Illinois (Chicago)0
Sea temperature
39°F sea temperature in January in Illinois (Chicago)39
37°F sea temperature in February in Illinois (Chicago)37
37°F sea temperature in March in Illinois (Chicago)37
37°F sea temperature in April in Illinois (Chicago)37
43°F sea temperature in May in Illinois (Chicago)43
54°F sea temperature in June in Illinois (Chicago)54
66°F sea temperature in July in Illinois (Chicago)66
70°F sea temperature in August in Illinois (Chicago)70
66°F sea temperature in September in Illinois (Chicago)66
57°F sea temperature in October in Illinois (Chicago)57
48°F sea temperature in November in Illinois (Chicago)48
41°F sea temperature in December in Illinois (Chicago)41

Note: 0 = None, L = Low, M = Moderate, H = High, VH = Very high, E = Extreme

Sunshine & UV index in Illinois

  Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Daily hours of sunshine
Daily hours of daylight
10 hours of daylight per day in January in Illinois (Chicago)10
11 hours of daylight per day in February in Illinois (Chicago)11
12 hours of daylight per day in March in Illinois (Chicago)12
13 hours of daylight per day in April in Illinois (Chicago)13
15 hours of daylight per day in May in Illinois (Chicago)15
15 hours of daylight per day in June in Illinois (Chicago)15
15 hours of daylight per day in July in Illinois (Chicago)15
14 hours of daylight per day in August in Illinois (Chicago)14
12 hours of daylight per day in September in Illinois (Chicago)12
11 hours of daylight per day in October in Illinois (Chicago)11
10 hours of daylight per day in November in Illinois (Chicago)10
9 hours of daylight per day in December in Illinois (Chicago)9
UV Index (Maximum)
UV (maximum) index 1 (Low) in January in Illinois (Chicago)1
UV (maximum) index 2 (Low) in February in Illinois (Chicago)2
UV (maximum) index 4 (Moderate) in March in Illinois (Chicago)4
UV (maximum) index 6 (High) in April in Illinois (Chicago)6
UV (maximum) index 7 (High) in May in Illinois (Chicago)7
UV (maximum) index 9 (Very High) in June in Illinois (Chicago)9
UV (maximum) index 9 (Very High) in July in Illinois (Chicago)9
UV (maximum) index 8 (Very High) in August in Illinois (Chicago)8
UV (maximum) index 6 (High) in September in Illinois (Chicago)6
UV (maximum) index 4 (Moderate) in October in Illinois (Chicago)4
UV (maximum) index 2 (Low) in November in Illinois (Chicago)2
UV (maximum) index 1 (Low) in December in Illinois (Chicago)1

Rainfall in Illinois

  Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Number of days with some rain
12 days with some rainfall in January in Illinois (Chicago)12
10 days with some rainfall in February in Illinois (Chicago)10
13 days with some rainfall in March in Illinois (Chicago)13
13 days with some rainfall in April in Illinois (Chicago)13
11 days with some rainfall in May in Illinois (Chicago)11
10 days with some rainfall in June in Illinois (Chicago)10
10 days with some rainfall in July in Illinois (Chicago)10
9 days with some rainfall in August in Illinois (Chicago)9
9 days with some rainfall in September in Illinois (Chicago)9
9 days with some rainfall in October in Illinois (Chicago)9
11 days with some rainfall in November in Illinois (Chicago)11
12 days with some rainfall in December in Illinois (Chicago)12
Average monthly rainfall (inches)
1.7 inches monthly rainfall in January in Illinois (Chicago)1.7
1.5 inches monthly rainfall in February in Illinois (Chicago)1.5
2.6 inches monthly rainfall in March in Illinois (Chicago)2.6
3.8 inches monthly rainfall in April in Illinois (Chicago)3.8
3.3 inches monthly rainfall in May in Illinois (Chicago)3.3
3.8 inches monthly rainfall in June in Illinois (Chicago)3.8
3.9 inches monthly rainfall in July in Illinois (Chicago)3.9
3.8 inches monthly rainfall in August in Illinois (Chicago)3.8
3.4 inches monthly rainfall in September in Illinois (Chicago)3.4
2.7 inches monthly rainfall in October in Illinois (Chicago)2.7
2.8 inches monthly rainfall in November in Illinois (Chicago)2.8
2.4 inches monthly rainfall in December in Illinois (Chicago)2.4

Compare Illinois weather with the UK

The weather chart below compares the average monthly 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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