Plymouth weather by month
What a typical year looks like in Plymouth, Illinois: average highs and lows, rain and snow, and the warmest and coldest days on record. Normals are the 1991–2020 averages at Bentley, 18 km from Plymouth; records cover 1972–2026.
The year at a glance
- Precipitation a year
- 40.1 in1019 mm
- Snow a year
- 23 in59 cm
- Last spring freeze
- Apr 15
- First fall freeze
- Oct 16
- Heating degree days
- 5,589
- Cooling degree days
- 1,170
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 97°36° (cooling, 1%).
Month by month
Plymouth in January
Highs average 34°1° and lows 18°−8°, with 1.7 in42 mm of precipitation and 8 in19 cm of snow in a typical January.
- Record high
- 68°20° (2008)
- Record low
- −22°−30° (1999)
- Heating degree days
- 1215
- Cooling degree days
- 0
Plymouth in February
Highs average 39°4° and lows 22°−6°, with 2 in50 mm of precipitation and 6 in16 cm of snow in a typical February.
- Record high
- 80°27° (2024)
- Record low
- −20°−29° (1996)
- Heating degree days
- 971
- Cooling degree days
- 0
Plymouth in March
Highs average 51°11° and lows 32°0°, with 2.6 in65 mm of precipitation and 2.1 in5.3 cm of snow in a typical March.
- Record high
- 92°33° (2026)
- Record low
- −7°−22° (1998)
- Heating degree days
- 734
- Cooling degree days
- 2
Plymouth in April
Highs average 63°17° and lows 42°6°, with 4.1 in104 mm of precipitation and 0.4 in1 cm of snow in a typical April.
- Record high
- 89°32° (2002)
- Record low
- 6°−14° (2018)
- Heating degree days
- 383
- Cooling degree days
- 16
Plymouth in May
Highs average 74°23° and lows 53°12°, with 5.3 in134 mm of precipitation in a typical May.
- Record high
- 97°36° (2018)
- Record low
- 29°−2° (2005)
- Heating degree days
- 134
- Cooling degree days
- 89
Plymouth in June
Highs average 83°28° and lows 63°17°, with 4.9 in123 mm of precipitation in a typical June.
- Record high
- 100°38° (2012)
- Record low
- 44°7° (2003)
- Heating degree days
- 12
- Cooling degree days
- 254
Plymouth in July
Highs average 86°30° and lows 67°19°, with 4.3 in109 mm of precipitation in a typical July.
- Record high
- 105°41° (2005)
- Record low
- 48°9° (1997)
- Heating degree days
- 1
- Cooling degree days
- 355
Plymouth in August
Highs average 85°29° and lows 64°18°, with 4.2 in106 mm of precipitation in a typical August.
- Record high
- 104°40° (2007)
- Record low
- 43°6° (2001)
- Heating degree days
- 4
- Cooling degree days
- 294
Plymouth in September
Highs average 79°26° and lows 56°13°, with 3.7 in93 mm of precipitation in a typical September.
- Record high
- 104°40° (2011)
- Record low
- 29°−2° (1995)
- Heating degree days
- 71
- Cooling degree days
- 135
Plymouth in OctoberThis month
Highs average 66°19° and lows 44°7°, with 3.2 in80 mm of precipitation and 0.1 in0.3 cm of snow in a typical October.
- Record high
- 96°36° (2006)
- Record low
- 18°−8° (1997)
- Heating degree days
- 332
- Cooling degree days
- 24
Plymouth in November
Highs average 51°11° and lows 33°0°, with 2.5 in62 mm of precipitation and 1.4 in3.6 cm of snow in a typical November.
- Record high
- 82°28° (2000)
- Record low
- 6°−14° (2019)
- Heating degree days
- 689
- Cooling degree days
- 1
Plymouth in December
Highs average 39°4° and lows 24°−5°, with 1.9 in48 mm of precipitation and 5 in13 cm of snow in a typical December.
- Record high
- 75°24° (2021)
- Record low
- −10°−23° (1998)
- Heating degree days
- 1043
- Cooling degree days
- 0