McLean weather by month
What a typical year looks like in McLean, Illinois: average highs and lows, rain and snow, and the warmest and coldest days on record. Normals are the 1991–2020 averages at LINCOLN, 23 km from McLean; records cover 1906–2026.
The year at a glance
- Precipitation a year
- 39.8 in1012 mm
- Snow a year
- 19 in49 cm
- Last spring freeze
- Apr 16
- First fall freeze
- Oct 12
- Heating degree days
- 5,624
- Cooling degree days
- 1,014
Freeze dates are medians (half of years earlier, half later). Degree days use a 65°F base; HVAC design temperatures here are −4°−20° (heating, 99%) and 95°35° (cooling, 1%).
Month by month
McLean in January
Highs average 35°1° and lows 18°−8°, with 2.2 in55 mm of precipitation and 6 in14 cm of snow in a typical January.
- Record high
- 70°21° (1907)
- Record low
- −34°−37° (1927)
- Heating degree days
- 1204
- Cooling degree days
- 0
McLean in February
Highs average 40°4° and lows 22°−6°, with 1.9 in49 mm of precipitation and 6 in16 cm of snow in a typical February.
- Record high
- 78°26° (2024)
- Record low
- −23°−31° (1934)
- Heating degree days
- 964
- Cooling degree days
- 0
McLean in March
Highs average 52°11° and lows 31°0°, with 2.7 in69 mm of precipitation and 1.8 in4.6 cm of snow in a typical March.
- Record high
- 91°33° (2026)
- Record low
- −14°−26° (1934)
- Heating degree days
- 734
- Cooling degree days
- 2
McLean in April
Highs average 64°18° and lows 41°5°, with 4.2 in108 mm of precipitation in a typical April.
- Record high
- 93°34° (1930)
- Record low
- −1°−18° (2018)
- Heating degree days
- 383
- Cooling degree days
- 11
McLean in May
Highs average 75°24° and lows 52°11°, with 4.4 in111 mm of precipitation in a typical May.
- Record high
- 102°39° (1934)
- Record low
- 24°−4° (1966)
- Heating degree days
- 132
- Cooling degree days
- 88
McLean in June
Highs average 83°29° and lows 61°16°, with 4.2 in106 mm of precipitation in a typical June.
- Record high
- 105°41° (1934)
- Record low
- 35°2° (1913)
- Heating degree days
- 15
- Cooling degree days
- 234
McLean in July
Highs average 86°30° and lows 64°18°, with 4.9 in125 mm of precipitation in a typical July.
- Record high
- 113°45° (1936)
- Record low
- 41°5° (1930)
- Heating degree days
- 2
- Cooling degree days
- 301
McLean in August
Highs average 84°29° and lows 61°16°, with 3.5 in88 mm of precipitation in a typical August.
- Record high
- 106°41° (1934)
- Record low
- 36°2° (1915)
- Heating degree days
- 6
- Cooling degree days
- 243
McLean in September
Highs average 79°26° and lows 53°12°, with 3.3 in84 mm of precipitation in a typical September.
- Record high
- 104°40° (1954)
- Record low
- 22°−6° (1928)
- Heating degree days
- 78
- Cooling degree days
- 117
McLean in OctoberThis month
Highs average 66°19° and lows 42°5°, with 3.4 in87 mm of precipitation and 0.1 in0.3 cm of snow in a typical October.
- Record high
- 95°35° (1953)
- Record low
- 7°−14° (1925)
- Heating degree days
- 357
- Cooling degree days
- 17
McLean in November
Highs average 51°11° and lows 32°0°, with 2.9 in73 mm of precipitation and 0.6 in1.5 cm of snow in a typical November.
- Record high
- 83°28° (1950)
- Record low
- −3°−19° (1930)
- Heating degree days
- 700
- Cooling degree days
- 1
McLean in December
Highs average 39°4° and lows 23°−5°, with 2.3 in58 mm of precipitation and 5 in12 cm of snow in a typical December.
- Record high
- 72°22° (1970)
- Record low
- −29°−34° (1914)
- Heating degree days
- 1049
- Cooling degree days
- 0