Prairie du Rocher weather by month
What a typical year looks like in Prairie du Rocher, Illinois: average highs and lows, rain and snow, and the warmest and coldest days on record. Normals are the 1991–2020 averages at Kaskaskia River Navigation Lock, 17 km from Prairie du Rocher; records cover 1974–2026.
The year at a glance
- Precipitation a year
- 42.8 in1088 mm
- Snow a year
- 4 in11 cm
- Last spring freeze
- Apr 5
- First fall freeze
- Oct 29
- Heating degree days
- 4,575
- Cooling degree days
- 1,460
Freeze dates are medians (half of years earlier, half later). Degree days use a 65°F base; HVAC design temperatures here are 5°−15° (heating, 99%) and 99°37° (cooling, 1%).
Month by month
Prairie du Rocher in January
Highs average 40°5° and lows 24°−4°, with 2.7 in69 mm of precipitation and 1.4 in3.6 cm of snow in a typical January.
- Record high
- 74°23° (1986)
- Record low
- −18°−28° (1985)
- Heating degree days
- 1016
- Cooling degree days
- 0
Prairie du Rocher in February
Highs average 46°8° and lows 27°−3°, with 2.4 in60 mm of precipitation and 1.5 in3.8 cm of snow in a typical February.
- Record high
- 84°29° (2024)
- Record low
- −14°−26° (1985)
- Heating degree days
- 798
- Cooling degree days
- 0
Prairie du Rocher in March
Highs average 56°13° and lows 35°2°, with 3.4 in87 mm of precipitation and 0.1 in0.3 cm of snow in a typical March.
- Record high
- 92°33° (2026)
- Record low
- −4°−20° (1978)
- Heating degree days
- 606
- Cooling degree days
- 3
Prairie du Rocher in April
Highs average 68°20° and lows 44°7°, with 4.7 in119 mm of precipitation in a typical April.
- Record high
- 99°37° (1989)
- Record low
- 22°−6° (2007)
- Heating degree days
- 298
- Cooling degree days
- 22
Prairie du Rocher in May
Highs average 77°25° and lows 55°13°, with 5.2 in132 mm of precipitation in a typical May.
- Record high
- 98°37° (1998)
- Record low
- 31°−1° (1976)
- Heating degree days
- 89
- Cooling degree days
- 119
Prairie du Rocher in June
Highs average 86°30° and lows 64°18°, with 4.1 in105 mm of precipitation in a typical June.
- Record high
- 109°43° (2012)
- Record low
- 44°7° (1988)
- Heating degree days
- 5
- Cooling degree days
- 308
Prairie du Rocher in July
Highs average 89°32° and lows 68°20°, with 4.1 in105 mm of precipitation in a typical July.
- Record high
- 109°43° (1987)
- Record low
- 51°11° (2004)
- Heating degree days
- 0
- Cooling degree days
- 425
Prairie du Rocher in August
Highs average 88°31° and lows 66°19°, with 3.3 in85 mm of precipitation in a typical August.
- Record high
- 109°43° (1988)
- Record low
- 41°5° (1986)
- Heating degree days
- 2
- Cooling degree days
- 364
Prairie du Rocher in September
Highs average 81°27° and lows 58°14°, with 2.9 in75 mm of precipitation in a typical September.
- Record high
- 112°44° (1990)
- Record low
- 32°0° (1984)
- Heating degree days
- 43
- Cooling degree days
- 180
Prairie du Rocher in OctoberThis month
Highs average 70°21° and lows 46°8°, with 3.1 in78 mm of precipitation in a typical October.
- Record high
- 96°36° (1989)
- Record low
- 23°−5° (1981)
- Heating degree days
- 256
- Cooling degree days
- 37
Prairie du Rocher in November
Highs average 56°13° and lows 37°3°, with 4 in102 mm of precipitation and 0.4 in1 cm of snow in a typical November.
- Record high
- 89°32° (1990)
- Record low
- 8°−13° (1976)
- Heating degree days
- 571
- Cooling degree days
- 2
Prairie du Rocher in December
Highs average 44°7° and lows 28°−2°, with 2.9 in72 mm of precipitation and 0.9 in2.3 cm of snow in a typical December.
- Record high
- 78°26° (1988)
- Record low
- −18°−28° (1989)
- Heating degree days
- 891
- Cooling degree days
- 0