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Decatur August Weather

Averages and records for weather in Decatur, Illinois in the month of August.

Typical Decatur August Weather 1991–2020
Average daily high	84.8 °F
Average daily low	64.8 °F
Average monthly precipitation	3.5 inches
Average monthly snow	none
Daily chance of precipitation	24.8%
Daily chance of snow	0%

Decatur August Weather Records 1893–2024
Highest temperature	106 °F	August 20, 1983
Lowest temperature	35 °F	August 29, 1986
Highest daily low	80 °F	August 19, 1936
Lowest daily high	65 °F	August 19, 1963
Hottest average high temperature	95.2 °F	1983
Coldest average high temperature	80.3 °F	1946
Most daily precipitation	4.7 inches	August 2, 1978
Most monthly precipitation	11.0 inches	1981
Most daily snow	none	-
Most monthly snow	none	-

Note: Daily averages are a moving average which includes 14 days before and after

Day	Average (°F)		Record (°F)
Day	High	Low	High	Low
August 1	85.3	65.8	102	49
August 2	85.2	65.7	103	52
August 3	85.1	65.6	103	47
August 4	85.1	65.5	104	45
August 5	85.0	65.4	105	50
August 6	84.9	65.3	102	49
August 7	84.8	65.1	102	44
August 8	84.8	65.2	105	47
August 9	84.8	65.1	106	48
August 10	84.8	65.0	100	52
August 11	84.8	65.0	101	50
August 12	84.9	65.0	101	46
August 13	84.9	65.0	102	48
August 14	85.0	65.0	97	45
August 15	85.0	65.0	101	45
August 16	84.9	64.9	105	45
August 17	84.8	64.9	104	51
August 18	84.6	64.7	105	46
August 19	84.6	64.6	102	49
August 20	84.7	64.6	106	43
August 21	84.7	64.4	102	43
August 22	84.6	64.3	102	49
August 23	84.6	64.1	100	46
August 24	84.4	64.0	100	46
August 25	84.3	63.8	100	44
August 26	84.1	63.7	103	44
August 27	84.0	63.5	101	45
August 28	84.0	63.3	99	37
August 29	83.9	63.2	100	35
August 30	83.8	63.0	98	40
August 31	83.6	62.8	100	40

Weather Station Details

Years	Station	Coordinates
1893–2024	Decatur WTP	location