Troy weather by month
What a typical year looks like in Troy, Illinois: average highs and lows, rain and snow, and the warmest and coldest days on record. Normals are the 1991–2020 averages at BELLEVILLE SIU RESEARCH, 24 km from Troy; records cover 1948–2026.
The year at a glance
- Precipitation a year
- 43.4 in1101 mm
- Snow a year
- 11 in28 cm
- Last spring freeze
- Apr 11
- First fall freeze
- Oct 13
- Heating degree days
- 4,208
- Cooling degree days
- 1,580
Freeze dates are medians (half of years earlier, half later). Degree days use a 65°F base; HVAC design temperatures here are 6°−14° (heating, 99%) and 98°37° (cooling, 1%).
Month by month
Troy in January
Highs average 43°6° and lows 24°−4°, with 2.6 in65 mm of precipitation and 3 in9 cm of snow in a typical January.
- Record high
- 75°24° (1950)
- Record low
- −27°−33° (1977)
- Heating degree days
- 973
- Cooling degree days
- 0
Troy in February
Highs average 49°9° and lows 28°−2°, with 2.2 in55 mm of precipitation and 3 in8 cm of snow in a typical February.
- Record high
- 83°28° (2018)
- Record low
- −21°−29° (1982)
- Heating degree days
- 748
- Cooling degree days
- 1
Troy in March
Highs average 59°15° and lows 36°2°, with 3.4 in87 mm of precipitation and 1 in2.5 cm of snow in a typical March.
- Record high
- 92°33° (2026)
- Record low
- −8°−22° (1978)
- Heating degree days
- 542
- Cooling degree days
- 8
Troy in April
Highs average 71°21° and lows 46°8°, with 4.9 in124 mm of precipitation in a typical April.
- Record high
- 91°33° (2006)
- Record low
- 18°−8° (2007)
- Heating degree days
- 236
- Cooling degree days
- 36
Troy in May
Highs average 79°26° and lows 56°13°, with 5.1 in128 mm of precipitation in a typical May.
- Record high
- 97°36° (1953)
- Record low
- 28°−2° (1976)
- Heating degree days
- 64
- Cooling degree days
- 148
Troy in June
Highs average 87°31° and lows 65°18°, with 4.6 in117 mm of precipitation in a typical June.
- Record high
- 106°41° (2012)
- Record low
- 38°3° (1972)
- Heating degree days
- 4
- Cooling degree days
- 331
Troy in July
Highs average 90°32° and lows 68°20°, with 4 in102 mm of precipitation in a typical July.
- Record high
- 110°43° (1954)
- Record low
- 43°6° (1972)
- Heating degree days
- 0
- Cooling degree days
- 434
Troy in August
Highs average 89°32° and lows 65°19°, with 3.9 in100 mm of precipitation in a typical August.
- Record high
- 105°41° (2007)
- Record low
- 39°4° (1986)
- Heating degree days
- 1
- Cooling degree days
- 379
Troy in September
Highs average 83°29° and lows 57°14°, with 3.4 in85 mm of precipitation in a typical September.
- Record high
- 103°39° (1954)
- Record low
- 26°−3° (1995)
- Heating degree days
- 36
- Cooling degree days
- 189
Troy in OctoberThis month
Highs average 73°23° and lows 47°8°, with 3.1 in79 mm of precipitation in a typical October.
- Record high
- 96°36° (2019)
- Record low
- 19°−7° (2024)
- Heating degree days
- 215
- Cooling degree days
- 49
Troy in November
Highs average 58°15° and lows 37°3°, with 3.6 in91 mm of precipitation and 0.6 in1.5 cm of snow in a typical November.
- Record high
- 84°29° (1950)
- Record low
- 2°−17° (1991)
- Heating degree days
- 530
- Cooling degree days
- 5
Troy in December
Highs average 46°8° and lows 28°−2°, with 2.6 in66 mm of precipitation and 2.9 in7.4 cm of snow in a typical December.
- Record high
- 78°26° (2025)
- Record low
- −19°−28° (1989)
- Heating degree days
- 859
- Cooling degree days
- 0