South Jacksonville weather by month
What a typical year looks like in South Jacksonville, Illinois: average highs and lows, rain and snow, and the warmest and coldest days on record. Normals are the 1991–2020 averages at JACKSONVILLE 2E, 5 km from South Jacksonville; records cover 1895–2026.
The year at a glance
- Precipitation a year
- 39.3 in997 mm
- Snow a year
- 16 in41 cm
- Last spring freeze
- Apr 19
- First fall freeze
- Oct 14
- Heating degree days
- 5,509
- Cooling degree days
- 1,066
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 95°35° (cooling, 1%).
Month by month
South Jacksonville in January
Highs average 36°2° and lows 18°−8°, with 1.9 in49 mm of precipitation and 5 in13 cm of snow in a typical January.
- Record high
- 75°24° (1950)
- Record low
- −24°−31° (1912)
- Heating degree days
- 1176
- Cooling degree days
- 0
South Jacksonville in February
Highs average 41°5° and lows 21°−6°, with 1.7 in44 mm of precipitation and 4 in11 cm of snow in a typical February.
- Record high
- 81°27° (2024)
- Record low
- −28°−33° (1934)
- Heating degree days
- 945
- Cooling degree days
- 0
South Jacksonville in March
Highs average 52°11° and lows 30°−1°, with 2.8 in71 mm of precipitation and 2 in5.1 cm of snow in a typical March.
- Record high
- 93°34° (2026)
- Record low
- −14°−26° (1948)
- Heating degree days
- 739
- Cooling degree days
- 2
South Jacksonville in April
Highs average 65°18° and lows 40°5°, with 4.3 in108 mm of precipitation and 0.3 in0.8 cm of snow in a typical April.
- Record high
- 94°34° (1930)
- Record low
- 10°−12° (1920)
- Heating degree days
- 385
- Cooling degree days
- 13
South Jacksonville in May
Highs average 75°24° and lows 52°11°, with 4.8 in122 mm of precipitation in a typical May.
- Record high
- 103°39° (1934)
- Record low
- 26°−3° (1966)
- Heating degree days
- 139
- Cooling degree days
- 85
South Jacksonville in June
Highs average 83°29° and lows 61°16°, with 4.9 in124 mm of precipitation in a typical June.
- Record high
- 107°42° (1931)
- Record low
- 36°2° (1993)
- Heating degree days
- 17
- Cooling degree days
- 228
South Jacksonville in July
Highs average 87°30° and lows 64°18°, with 4 in101 mm of precipitation in a typical July.
- Record high
- 114°46° (1954)
- Record low
- 43°6° (1911)
- Heating degree days
- 2
- Cooling degree days
- 320
South Jacksonville in August
Highs average 85°30° and lows 62°17°, with 3.4 in86 mm of precipitation in a typical August.
- Record high
- 112°44° (1934)
- Record low
- 39°4° (1915)
- Heating degree days
- 6
- Cooling degree days
- 267
South Jacksonville in September
Highs average 80°27° and lows 54°12°, with 3.5 in89 mm of precipitation in a typical September.
- Record high
- 106°41° (1899)
- Record low
- 23°−5° (1899)
- Heating degree days
- 75
- Cooling degree days
- 127
South Jacksonville in OctoberThis month
Highs average 68°20° and lows 42°6°, with 3 in75 mm of precipitation in a typical October.
- Record high
- 98°37° (1897)
- Record low
- 9°−13° (1925)
- Heating degree days
- 333
- Cooling degree days
- 23
South Jacksonville in November
Highs average 53°12° and lows 32°0°, with 3 in76 mm of precipitation and 1 in2.5 cm of snow in a typical November.
- Record high
- 84°29° (1937)
- Record low
- −5°−21° (1929)
- Heating degree days
- 677
- Cooling degree days
- 1
South Jacksonville in December
Highs average 41°5° and lows 23°−5°, with 2 in50 mm of precipitation and 4 in9 cm of snow in a typical December.
- Record high
- 74°23° (1998)
- Record low
- −21°−29° (1914)
- Heating degree days
- 1015
- Cooling degree days
- 0