Illinois climate guide

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
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

Sunshine & Daylight in Illinois

  Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Daily hours of sunshine
4 hours of sunshine per day (45% of daylight hours) in January in Illinois4
5 hours of sunshine per day (46% of daylight hours) in February in Illinois5
6 hours of sunshine per day (50% of daylight hours) in March in Illinois6
7 hours of sunshine per day (55% of daylight hours) in April in Illinois7
9 hours of sunshine per day (62% of daylight hours) in May in Illinois9
10 hours of sunshine per day (68% of daylight hours) in June in Illinois10
10 hours of sunshine per day (69% of daylight hours) in July in Illinois10
9 hours of sunshine per day (67% of daylight hours) in August in Illinois9
8 hours of sunshine per day (61% of daylight hours) in September in Illinois8
6 hours of sunshine per day (56% of daylight hours) in October in Illinois6
4 hours of sunshine per day (39% of daylight hours) in November in Illinois4
3 hours of sunshine per day (37% of daylight hours) in December in Illinois3
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

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

More climate for Illinois

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

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

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Check climate guides for Illinois showing average temperature, rainfall & sunshine figures for each month of the year. The climate guide shown above is for Chicago.

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More about Illinois

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

The climate guide for Illinois, represented by 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.

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

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