Decatur weather by month

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

Temperature
Rainfall
Sunshine & UV index

Temperature in Decatur (°C)

	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
Max temperature (daytime)	1	4	11	18	24	29	31	29	26	20	11	3
Min temperature (night-time)	-9	-7	-1	5	11	16	18	17	13	6	1	-6
Heat & Humidity	0	0	0	0	0	M	H	M	L	0	0	0

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

Sunshine & UV index in Decatur

	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
Daily hours of sunshine	5	5	6	8	9	10	10	9	8	7	4	4
Daily hours of daylight	10	11	12	13	14	15	15	14	12	11	10	9
UV Index (Maximum)	2	3	4	6	8	9	9	8	6	4	2	2

Rainfall in Decatur

	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
Number of days with some rain	10	9	12	12	10	9	9	8	8	8	10	11
Average monthly rainfall (mm)	49	48	80	96	102	100	107	93	81	70	77	72

More about Decatur

Decatur by month

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

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The climate guide for Illinois (Decatur) 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.

What's the climate like in Decatur?

Decatur has a cold climate with hot summers and some rainfall in all months.

Decatur weather in January

Expect daytime maximum temperatures of 1°C in Decatur, Illinois in January based on long-term weather averages. There are 5 hours of sunshine per day on average with 10 days with some rainfall and typically 49 mm of rainfall in the month, which might fall as snow.

1
1°C max day temperature
5
5 hours of sunshine per day
10
10 days with some rainfall
-9
-9°C min night temperature
10
10 hours of daylight per day
0
No heat & humidity
49
49 mm of monthly rainfall
2
2 (Low) UV index

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Decatur weather in February

Expect daytime maximum temperatures of 4°C in Decatur, Illinois in February based on long-term weather averages. There are 5 hours of sunshine per day on average with typically 48 mm of rainfall in the month, which might fall as snow.

4
4°C max day temperature
5
5 hours of sunshine per day
9
9 days with some rainfall
-7
-7°C min night temperature
11
11 hours of daylight per day
0
No heat & humidity
48
48 mm of monthly rainfall
3
3 (Moderate) UV index

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Decatur weather in March

Expect daytime maximum temperatures of 11°C in Decatur, Illinois in March based on long-term weather averages. There are 6 hours of sunshine per day on average with 12 days with some rainfall and typically 80 mm of rainfall in the month.

11
11°C max day temperature
6
6 hours of sunshine per day
12
12 days with some rainfall
-1
-1°C min night temperature
12
12 hours of daylight per day
0
No heat & humidity
80
80 mm of monthly rainfall
4
4 (Moderate) UV index

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Decatur weather in April

Expect daytime maximum temperatures of 18°C in Decatur, Illinois in April based on long-term weather averages. There are 8 hours of sunshine per day on average with 12 days with some rainfall and typically 96 mm of rainfall in the month.

18
18°C max day temperature
8
8 hours of sunshine per day
12
12 days with some rainfall
5
5°C min night temperature
13
13 hours of daylight per day
0
No heat & humidity
96
96 mm of monthly rainfall
6
6 (High) UV index

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Decatur weather in May

Expect daytime maximum temperatures of 24°C in Decatur, Illinois in May based on long-term weather averages. There are 9 hours of sunshine per day on average with 10 days with some rainfall and typically 102 mm of rainfall in the month.

24
24°C max day temperature
9
9 hours of sunshine per day
10
10 days with some rainfall
11
11°C min night temperature
14
14 hours of daylight per day
0
No heat & humidity
102
102 mm of monthly rainfall
8
8 (Very High) UV index

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Decatur weather in June

Expect daytime maximum temperatures of 29°C in Decatur, Illinois in June based on long-term weather averages. There are 10 hours of sunshine per day on average with typically 100 mm of rainfall in the month.

29
29°C max day temperature
10
10 hours of sunshine per day
9
9 days with some rainfall
16
16°C min night temperature
15
15 hours of daylight per day
M
Moderate heat & humidity
100
100 mm of monthly rainfall
9
9 (Very High) UV index

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Decatur weather in July

Expect daytime maximum temperatures of 31°C in Decatur, Illinois in July and high heat and humidity based on long-term weather averages. There are 10 hours of sunshine per day on average with typically 107 mm of rainfall in the month.

31
31°C max day temperature
10
10 hours of sunshine per day
9
9 days with some rainfall
18
18°C min night temperature
15
15 hours of daylight per day
H
High heat & humidity
107
107 mm of monthly rainfall
9
9 (Very High) UV index

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Decatur weather in August

Expect daytime maximum temperatures of 29°C in Decatur, Illinois in August based on long-term weather averages. There are 9 hours of sunshine per day on average with typically 93 mm of rainfall in the month.

29
29°C max day temperature
9
9 hours of sunshine per day
8
8 days with some rainfall
17
17°C min night temperature
14
14 hours of daylight per day
M
Moderate heat & humidity
93
93 mm of monthly rainfall
8
8 (Very High) UV index

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Decatur weather in September

Expect daytime maximum temperatures of 26°C in Decatur, Illinois in September based on long-term weather averages. There are 8 hours of sunshine per day on average with typically 81 mm of rainfall in the month.

26
26°C max day temperature
8
8 hours of sunshine per day
8
8 days with some rainfall
13
13°C min night temperature
12
12 hours of daylight per day
L
Low heat & humidity
81
81 mm of monthly rainfall
6
6 (High) UV index

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Decatur weather in October

Expect daytime maximum temperatures of 20°C in Decatur, Illinois in October based on long-term weather averages. There are 7 hours of sunshine per day on average with typically 70 mm of rainfall in the month.

20
20°C max day temperature
7
7 hours of sunshine per day
8
8 days with some rainfall
6
6°C min night temperature
11
11 hours of daylight per day
0
No heat & humidity
70
70 mm of monthly rainfall
4
4 (Moderate) UV index

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Decatur weather in November

Expect daytime maximum temperatures of 11°C in Decatur, Illinois in November based on long-term weather averages. There are 4 hours of sunshine per day on average with 10 days with some rainfall and typically 77 mm of rainfall in the month.

11
11°C max day temperature
4
4 hours of sunshine per day
10
10 days with some rainfall
1
1°C min night temperature
10
10 hours of daylight per day
0
No heat & humidity
77
77 mm of monthly rainfall
2
2 (Low) UV index

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Decatur weather in December

Expect daytime maximum temperatures of 3°C in Decatur, Illinois in December based on long-term weather averages. There are 4 hours of sunshine per day on average with 11 days with some rainfall and typically 72 mm of rainfall in the month, which might fall as snow.