Decatur weather by month
What a typical year looks like in Decatur, Indiana: average highs and lows, rain and snow, and the warmest and coldest days on record. Normals are the 1991–2020 averages at Berne Wwtp, 18 km from Decatur; records cover 1910–2026.
The year at a glance
- Precipitation a year
- 41.9 in1063 mm
- Snow a year
- 28 in71 cm
- Last spring freeze
- Apr 17
- First fall freeze
- Oct 22
- Heating degree days
- 6,033
- Cooling degree days
- 876
Freeze dates are medians (half of years earlier, half later). Degree days use a 65°F base; HVAC design temperatures here are −2°−19° (heating, 99%) and 93°34° (cooling, 1%).
Month by month
Decatur in January
Highs average 33°0° and lows 18°−8°, with 2.9 in73 mm of precipitation and 8 in21 cm of snow in a typical January.
- Record high
- 70°21° (1950)
- Record low
- −24°−31° (1985)
- Heating degree days
- 1229
- Cooling degree days
- 0
Decatur in February
Highs average 36°2° and lows 20°−7°, with 2.4 in62 mm of precipitation and 8 in20 cm of snow in a typical February.
- Record high
- 74°23° (2000)
- Record low
- −20°−29° (2014)
- Heating degree days
- 1033
- Cooling degree days
- 0
Decatur in March
Highs average 47°9° and lows 28°−2°, with 3 in77 mm of precipitation and 5 in12 cm of snow in a typical March.
- Record high
- 86°30° (2012)
- Record low
- −6°−21° (1943)
- Heating degree days
- 844
- Cooling degree days
- 1
Decatur in April
Highs average 61°16° and lows 39°4°, with 4 in101 mm of precipitation and 0.5 in1.3 cm of snow in a typical April.
- Record high
- 90°32° (1925)
- Record low
- 10°−12° (1982)
- Heating degree days
- 466
- Cooling degree days
- 7
Decatur in May
Highs average 72°22° and lows 51°11°, with 4.6 in117 mm of precipitation in a typical May.
- Record high
- 99°37° (1911)
- Record low
- 25°−4° (1943)
- Heating degree days
- 180
- Cooling degree days
- 65
Decatur in June
Highs average 81°27° and lows 61°16°, with 4.6 in116 mm of precipitation in a typical June.
- Record high
- 104°40° (1988)
- Record low
- 36°2° (1918)
- Heating degree days
- 24
- Cooling degree days
- 195
Decatur in July
Highs average 84°29° and lows 64°18°, with 4.6 in116 mm of precipitation in a typical July.
- Record high
- 107°42° (1934)
- Record low
- 42°6° (1930)
- Heating degree days
- 3
- Cooling degree days
- 279
Decatur in August
Highs average 82°28° and lows 62°17°, with 3.9 in99 mm of precipitation in a typical August.
- Record high
- 105°41° (1918)
- Record low
- 37°3° (1965)
- Heating degree days
- 8
- Cooling degree days
- 217
Decatur in September
Highs average 76°25° and lows 54°12°, with 3.2 in81 mm of precipitation in a typical September.
- Record high
- 101°38° (1939)
- Record low
- 27°−3° (1942)
- Heating degree days
- 89
- Cooling degree days
- 98
Decatur in OctoberThis month
Highs average 64°18° and lows 43°6°, with 3 in75 mm of precipitation and 0.1 in0.3 cm of snow in a typical October.
- Record high
- 90°32° (1922)
- Record low
- 16°−9° (1925)
- Heating degree days
- 374
- Cooling degree days
- 14
Decatur in November
Highs average 50°10° and lows 33°0°, with 3.1 in78 mm of precipitation and 1.4 in3.6 cm of snow in a typical November.
- Record high
- 80°27° (2016)
- Record low
- −3°−19° (1929)
- Heating degree days
- 720
- Cooling degree days
- 0
Decatur in December
Highs average 38°3° and lows 24°−5°, with 2.7 in68 mm of precipitation and 5 in13 cm of snow in a typical December.
- Record high
- 72°22° (1998)
- Record low
- −19°−28° (1989)
- Heating degree days
- 1063
- Cooling degree days
- 0