Harrisburg weather by month
What a typical year looks like in Harrisburg, Illinois: average highs and lows, rain and snow, and the warmest and coldest days on record. Normals are the 1991–2020 averages at Harrisburg, 2 km from Harrisburg; records cover 1888–2026.
The year at a glance
- Precipitation a year
- 47.6 in1209 mm
- Snow a year
- Rare
- Last spring freeze
- Apr 5
- First fall freeze
- Oct 22
- Heating degree days
- 4,299
- Cooling degree days
- 1,521
Freeze dates are medians (half of years earlier, half later). Degree days use a 65°F base; HVAC design temperatures here are 7°−14° (heating, 99%) and 97°36° (cooling, 1%).
Month by month
Harrisburg in January
Highs average 43°6° and lows 24°−4°, with 3.8 in96 mm of precipitation in a typical January.
- Record high
- 78°26° (1943)
- Record low
- −22°−30° (1977)
- Heating degree days
- 978
- Cooling degree days
- 0
Harrisburg in February
Highs average 48°9° and lows 28°−2°, with 3.1 in80 mm of precipitation in a typical February.
- Record high
- 80°27° (1918)
- Record low
- −23°−31° (1951)
- Heating degree days
- 756
- Cooling degree days
- 0
Harrisburg in March
Highs average 58°15° and lows 36°2°, with 4.9 in124 mm of precipitation in a typical March.
- Record high
- 94°34° (1929)
- Record low
- −8°−22° (1960)
- Heating degree days
- 563
- Cooling degree days
- 8
Harrisburg in April
Highs average 69°21° and lows 46°8°, with 5.3 in134 mm of precipitation in a typical April.
- Record high
- 96°36° (1901)
- Record low
- 22°−6° (1923)
- Heating degree days
- 260
- Cooling degree days
- 36
Harrisburg in May
Highs average 78°26° and lows 57°14°, with 4.3 in109 mm of precipitation in a typical May.
- Record high
- 100°38° (1911)
- Record low
- 28°−2° (2005)
- Heating degree days
- 66
- Cooling degree days
- 139
Harrisburg in June
Highs average 86°30° and lows 65°18°, with 4.9 in125 mm of precipitation in a typical June.
- Record high
- 106°41° (1913)
- Record low
- 40°4° (1917)
- Heating degree days
- 5
- Cooling degree days
- 322
Harrisburg in July
Highs average 89°32° and lows 68°20°, with 3.5 in89 mm of precipitation in a typical July.
- Record high
- 113°45° (1936)
- Record low
- 45°7° (1997)
- Heating degree days
- 0
- Cooling degree days
- 426
Harrisburg in August
Highs average 88°31° and lows 66°19°, with 3.6 in91 mm of precipitation in a typical August.
- Record high
- 111°44° (1930)
- Record low
- 41°5° (2009)
- Heating degree days
- 2
- Cooling degree days
- 370
Harrisburg in September
Highs average 82°28° and lows 57°14°, with 3.1 in79 mm of precipitation in a typical September.
- Record high
- 109°43° (1913)
- Record low
- 23°−5° (1995)
- Heating degree days
- 37
- Cooling degree days
- 183
Harrisburg in OctoberThis month
Highs average 71°22° and lows 45°7°, with 3.8 in96 mm of precipitation in a typical October.
- Record high
- 98°37° (1953)
- Record low
- 18°−8° (1981)
- Heating degree days
- 242
- Cooling degree days
- 34
Harrisburg in November
Highs average 57°14° and lows 36°2°, with 4 in101 mm of precipitation in a typical November.
- Record high
- 87°31° (1909)
- Record low
- −3°−19° (1929)
- Heating degree days
- 548
- Cooling degree days
- 3
Harrisburg in December
Highs average 47°8° and lows 29°−2°, with 3.4 in86 mm of precipitation in a typical December.
- Record high
- 78°26° (1982)
- Record low
- −11°−24° (1917)
- Heating degree days
- 842
- Cooling degree days
- 0