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 °C
-1°C maximum daytime temperature in January in Chicago-1
1°C maximum daytime temperature in February in Chicago1
8°C maximum daytime temperature in March in Chicago8
15°C maximum daytime temperature in April in Chicago15
21°C maximum daytime temperature in May in Chicago21
27°C maximum daytime temperature in June in Chicago27
29°C maximum daytime temperature in July in Chicago29
28°C maximum daytime temperature in August in Chicago28
24°C maximum daytime temperature in September in Chicago24
17°C maximum daytime temperature in October in Chicago17
9°C maximum daytime temperature in November in Chicago9
2°C maximum daytime temperature in December in Chicago2
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 °C
4°C sea temperature in January in Chicago4
3°C sea temperature in February in Chicago3
3°C sea temperature in March in Chicago3
3°C sea temperature in April in Chicago3
6°C sea temperature in May in Chicago6
12°C sea temperature in June in Chicago12
19°C sea temperature in July in Chicago19
21°C sea temperature in August in Chicago21
19°C sea temperature in September in Chicago19
14°C sea temperature in October in Chicago14
9°C sea temperature in November in Chicago9
5°C sea temperature in December in Chicago5

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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 / mm)  |  Imperial (°F / inches)

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Illinois weather averages

Temperature in Illinois (°C)

  Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Max temperature (daytime)
-1°C maximum daytime temperature in January in Illinois (Chicago)-1
1°C maximum daytime temperature in February in Illinois (Chicago)1
8°C maximum daytime temperature in March in Illinois (Chicago)8
15°C maximum daytime temperature in April in Illinois (Chicago)15
21°C maximum daytime temperature in May in Illinois (Chicago)21
27°C maximum daytime temperature in June in Illinois (Chicago)27
29°C maximum daytime temperature in July in Illinois (Chicago)29
28°C maximum daytime temperature in August in Illinois (Chicago)28
24°C maximum daytime temperature in September in Illinois (Chicago)24
17°C maximum daytime temperature in October in Illinois (Chicago)17
9°C maximum daytime temperature in November in Illinois (Chicago)9
2°C maximum daytime temperature in December in Illinois (Chicago)2
Min temperature (night-time)
-10°C minimum night-time temperature in January in Illinois (Chicago)-10
-8°C minimum night-time temperature in February in Illinois (Chicago)-8
-2°C minimum night-time temperature in March in Illinois (Chicago)-2
3°C minimum night-time temperature in April in Illinois (Chicago)3
9°C minimum night-time temperature in May in Illinois (Chicago)9
14°C minimum night-time temperature in June in Illinois (Chicago)14
17°C minimum night-time temperature in July in Illinois (Chicago)17
16°C minimum night-time temperature in August in Illinois (Chicago)16
12°C minimum night-time temperature in September in Illinois (Chicago)12
6°C minimum night-time temperature in October in Illinois (Chicago)6
0°C minimum night-time temperature in November in Illinois (Chicago)0
-7°C minimum night-time temperature in December in Illinois (Chicago)-7
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
4°C sea temperature in January in Illinois (Chicago)4
3°C sea temperature in February in Illinois (Chicago)3
3°C sea temperature in March in Illinois (Chicago)3
3°C sea temperature in April in Illinois (Chicago)3
6°C sea temperature in May in Illinois (Chicago)6
12°C sea temperature in June in Illinois (Chicago)12
19°C sea temperature in July in Illinois (Chicago)19
21°C sea temperature in August in Illinois (Chicago)21
19°C sea temperature in September in Illinois (Chicago)19
14°C sea temperature in October in Illinois (Chicago)14
9°C sea temperature in November in Illinois (Chicago)9
5°C sea temperature in December in Illinois (Chicago)5

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 (mm)
44 mm monthly rainfall in January in Illinois (Chicago)44
38 mm monthly rainfall in February in Illinois (Chicago)38
67 mm monthly rainfall in March in Illinois (Chicago)67
96 mm monthly rainfall in April in Illinois (Chicago)96
84 mm monthly rainfall in May in Illinois (Chicago)84
96 mm monthly rainfall in June in Illinois (Chicago)96
100 mm monthly rainfall in July in Illinois (Chicago)100
97 mm monthly rainfall in August in Illinois (Chicago)97
87 mm monthly rainfall in September in Illinois (Chicago)87
68 mm monthly rainfall in October in Illinois (Chicago)68
72 mm monthly rainfall in November in Illinois (Chicago)72
62 mm monthly rainfall in December in Illinois (Chicago)62

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 (°C)

Illinois, USA (Chicago)
UK (London)
7
1
7
8
10
15
13
21
17
27
20
29
22
28
22
24
19
17
15
9
10
2
8
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
-1

Metric (°C / mm)  |  Imperial (°F / inches)

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