Simpson weather by month
What a typical year looks like in Simpson, Illinois: average highs and lows, rain and snow, and the warmest and coldest days on record. Normals are the 1991–2020 averages at Dixon Springs Agric Cntr, 9 km from Simpson; records cover 1941–2026.
The year at a glance
- Precipitation a year
- 50.5 in1283 mm
- Snow a year
- 7 in18 cm
- Last spring freeze
- Apr 9
- First fall freeze
- Oct 21
- Heating degree days
- 4,206
- Cooling degree days
- 1,388
Freeze dates are medians (half of years earlier, half later). Degree days use a 65°F base; HVAC design temperatures here are 8°−13° (heating, 99%) and 97°36° (cooling, 1%).
Month by month
Simpson in January
Highs average 43°6° and lows 26°−4°, with 3.8 in98 mm of precipitation and 1.7 in4.3 cm of snow in a typical January.
- Record high
- 76°24° (1943)
- Record low
- −20°−29° (1977)
- Heating degree days
- 948
- Cooling degree days
- 0
Simpson in February
Highs average 49°9° and lows 29°−2°, with 3.6 in92 mm of precipitation and 3 in8 cm of snow in a typical February.
- Record high
- 78°26° (1996)
- Record low
- −10°−23° (1996)
- Heating degree days
- 732
- Cooling degree days
- 0
Simpson in March
Highs average 59°15° and lows 37°3°, with 4.7 in118 mm of precipitation and 0.6 in1.5 cm of snow in a typical March.
- Record high
- 86°30° (2026)
- Record low
- −3°−19° (1978)
- Heating degree days
- 540
- Cooling degree days
- 5
Simpson in April
Highs average 70°21° and lows 46°8°, with 5 in126 mm of precipitation in a typical April.
- Record high
- 89°32° (1987)
- Record low
- 20°−7° (1943)
- Heating degree days
- 242
- Cooling degree days
- 30
Simpson in May
Highs average 77°25° and lows 56°13°, with 5.2 in132 mm of precipitation in a typical May.
- Record high
- 94°34° (2012)
- Record low
- 29°−2° (1976)
- Heating degree days
- 79
- Cooling degree days
- 122
Simpson in June
Highs average 85°30° and lows 63°17°, with 4.1 in104 mm of precipitation in a typical June.
- Record high
- 107°42° (2012)
- Record low
- 39°4° (1972)
- Heating degree days
- 7
- Cooling degree days
- 279
Simpson in July
Highs average 88°31° and lows 67°19°, with 4.4 in112 mm of precipitation in a typical July.
- Record high
- 105°41° (2011)
- Record low
- 46°8° (1971)
- Heating degree days
- 0
- Cooling degree days
- 384
Simpson in August
Highs average 87°31° and lows 65°18°, with 3.7 in93 mm of precipitation in a typical August.
- Record high
- 103°39° (2007)
- Record low
- 46°8° (1986)
- Heating degree days
- 2
- Cooling degree days
- 346
Simpson in September
Highs average 82°28° and lows 58°14°, with 3.8 in96 mm of precipitation in a typical September.
- Record high
- 102°39° (1947)
- Record low
- 32°0° (1983)
- Heating degree days
- 38
- Cooling degree days
- 180
Simpson in OctoberThis month
Highs average 71°22° and lows 46°8°, with 3.8 in98 mm of precipitation and 0.3 in0.8 cm of snow in a typical October.
- Record high
- 94°34° (2019)
- Record low
- 17°−8° (1981)
- Heating degree days
- 233
- Cooling degree days
- 39
Simpson in November
Highs average 57°14° and lows 37°3°, with 4.3 in109 mm of precipitation in a typical November.
- Record high
- 83°28° (1971)
- Record low
- 5°−15° (2019)
- Heating degree days
- 540
- Cooling degree days
- 3
Simpson in December
Highs average 46°8° and lows 29°−2°, with 4.2 in106 mm of precipitation and 1.4 in3.6 cm of snow in a typical December.
- Record high
- 77°25° (1982)
- Record low
- −14°−26° (1989)
- Heating degree days
- 845
- Cooling degree days
- 0