Garrison weather by month
What a typical year looks like in Garrison, Montana: average highs and lows, rain and snow, and the warmest and coldest days on record. Normals are the 1991–2020 averages at Deer Lodge 3 W, 17 km from Garrison; records cover 1893–2026.
The year at a glance
- Precipitation a year
- 14.6 in370 mm
- Snow a year
- Rare
- Last spring freeze
- Jun 20
- First fall freeze
- Aug 22
- Heating degree days
- 9,030
- Cooling degree days
- 66
Freeze dates are medians (half of years earlier, half later). Degree days use a 65°F base; HVAC design temperatures here are −17°−27° (heating, 99%) and 91°33° (cooling, 1%).
Month by month
Garrison in January
Highs average 33°1° and lows 11°−12°, with 0.48 in12 mm of precipitation in a typical January.
- Record high
- 62°17° (2015)
- Record low
- −40° (2024)
- Heating degree days
- 1334
- Cooling degree days
- 0
Garrison in February
Highs average 36°2° and lows 13°−10°, with 0.68 in17 mm of precipitation in a typical February.
- Record high
- 69°21° (1932)
- Record low
- −41° (1899)
- Heating degree days
- 1133
- Cooling degree days
- 0
Garrison in March
Highs average 44°7° and lows 19°−7°, with 1.3 in33 mm of precipitation in a typical March.
- Record high
- 73°23° (1895)
- Record low
- −29°−34° (2019)
- Heating degree days
- 1029
- Cooling degree days
- 0
Garrison in April
Highs average 53°12° and lows 26°−3°, with 1.1 in27 mm of precipitation in a typical April.
- Record high
- 84°29° (1946)
- Record low
- −8°−22° (1982)
- Heating degree days
- 769
- Cooling degree days
- 0
Garrison in May
Highs average 62°17° and lows 34°1°, with 2.2 in56 mm of precipitation in a typical May.
- Record high
- 94°34° (1919)
- Record low
- 7°−14° (1967)
- Heating degree days
- 529
- Cooling degree days
- 1
Garrison in June
Highs average 69°20° and lows 40°4°, with 2.7 in68 mm of precipitation in a typical June.
- Record high
- 100°38° (1919)
- Record low
- 22°−6° (1969)
- Heating degree days
- 330
- Cooling degree days
- 4
Garrison in July
Highs average 79°26° and lows 44°7°, with 1.5 in38 mm of precipitation in a typical July.
- Record high
- 108°42° (1901)
- Record low
- 20°−7° (1997)
- Heating degree days
- 138
- Cooling degree days
- 34
Garrison in August
Highs average 79°26° and lows 42°6°, with 1.3 in34 mm of precipitation in a typical August.
- Record high
- 103°39° (1919)
- Record low
- 19°−7° (1995)
- Heating degree days
- 155
- Cooling degree days
- 25
Garrison in September
Highs average 70°21° and lows 35°1°, with 1.4 in34 mm of precipitation in a typical September.
- Record high
- 99°37° (1901)
- Record low
- 9°−13° (1985)
- Heating degree days
- 388
- Cooling degree days
- 2
Garrison in OctoberThis month
Highs average 55°13° and lows 26°−3°, with 1 in25 mm of precipitation in a typical October.
- Record high
- 87°31° (1992)
- Record low
- −15°−26° (2006)
- Heating degree days
- 756
- Cooling degree days
- 0
Garrison in November
Highs average 40°5° and lows 16°−9°, with 0.51 in13 mm of precipitation in a typical November.
- Record high
- 73°23° (1999)
- Record low
- −38°−39° (1959)
- Heating degree days
- 1102
- Cooling degree days
- 0
Garrison in December
Highs average 31°0° and lows 11°−12°, with 0.5 in13 mm of precipitation in a typical December.
- Record high
- 66°19° (1939)
- Record low
- −42°−41° (1919)
- Heating degree days
- 1367
- Cooling degree days
- 0