Grafton weather by month
What a typical year looks like in Grafton, Illinois: average highs and lows, rain and snow, and the warmest and coldest days on record. Normals are the 1991–2020 averages at ST CHARLES ELM POINT, 20 km from Grafton; records cover 1893–2026.
The year at a glance
- Precipitation a year
- 45.7 in1161 mm
- Snow a year
- 9 in23 cm
- Last spring freeze
- Apr 6
- First fall freeze
- Oct 25
- Heating degree days
- 4,806
- Cooling degree days
- 1,387
Freeze dates are medians (half of years earlier, half later). Degree days use a 65°F base; HVAC design temperatures here are 3°−16° (heating, 99%) and 96°36° (cooling, 1%).
Month by month
Grafton in January
Highs average 40°4° and lows 22°−6°, with 2.7 in70 mm of precipitation and 4 in11 cm of snow in a typical January.
- Record high
- 82°28° (2006)
- Record low
- −25°−32° (1894)
- Heating degree days
- 1063
- Cooling degree days
- 0
Grafton in February
Highs average 45°7° and lows 25°−4°, with 2.9 in73 mm of precipitation and 2.6 in6.6 cm of snow in a typical February.
- Record high
- 84°29° (2024)
- Record low
- −24°−31° (1905)
- Heating degree days
- 842
- Cooling degree days
- 0
Grafton in March
Highs average 55°13° and lows 34°1°, with 3.6 in92 mm of precipitation and 0.5 in1.3 cm of snow in a typical March.
- Record high
- 93°34° (1929)
- Record low
- −7°−22° (1978)
- Heating degree days
- 641
- Cooling degree days
- 4
Grafton in April
Highs average 67°19° and lows 44°7°, with 5.1 in130 mm of precipitation in a typical April.
- Record high
- 94°34° (1989)
- Record low
- 0°−18° (1947)
- Heating degree days
- 313
- Cooling degree days
- 25
Grafton in May
Highs average 76°24° and lows 55°13°, with 5.5 in138 mm of precipitation in a typical May.
- Record high
- 101°38° (1934)
- Record low
- 30°−1° (1903)
- Heating degree days
- 96
- Cooling degree days
- 113
Grafton in June
Highs average 84°29° and lows 64°18°, with 4.4 in110 mm of precipitation in a typical June.
- Record high
- 106°41° (1931)
- Record low
- 41°5° (1894)
- Heating degree days
- 9
- Cooling degree days
- 284
Grafton in July
Highs average 88°31° and lows 68°20°, with 4.2 in107 mm of precipitation in a typical July.
- Record high
- 115°46° (1954)
- Record low
- 47°8° (1972)
- Heating degree days
- 0
- Cooling degree days
- 408
Grafton in August
Highs average 87°30° and lows 66°19°, with 4.1 in103 mm of precipitation in a typical August.
- Record high
- 112°44° (1934)
- Record low
- 43°6° (1986)
- Heating degree days
- 2
- Cooling degree days
- 352
Grafton in September
Highs average 80°27° and lows 57°14°, with 3.1 in78 mm of precipitation in a typical September.
- Record high
- 106°41° (1954)
- Record low
- 31°−1° (1899)
- Heating degree days
- 49
- Cooling degree days
- 163
Grafton in OctoberThis month
Highs average 69°20° and lows 46°8°, with 3.5 in89 mm of precipitation in a typical October.
- Record high
- 97°36° (1953)
- Record low
- 19°−7° (1925)
- Heating degree days
- 275
- Cooling degree days
- 35
Grafton in November
Highs average 55°13° and lows 35°2°, with 3.7 in95 mm of precipitation and 0.1 in0.3 cm of snow in a typical November.
- Record high
- 87°31° (1937)
- Record low
- −4°−20° (1929)
- Heating degree days
- 594
- Cooling degree days
- 3
Grafton in December
Highs average 44°7° and lows 26°−3°, with 3 in76 mm of precipitation and 1.5 in3.8 cm of snow in a typical December.
- Record high
- 77°25° (1948)
- Record low
- −19°−28° (1901)
- Heating degree days
- 922
- Cooling degree days
- 0