Ismay weather by month
What a typical year looks like in Ismay, Montana: average highs and lows, rain and snow, and the warmest and coldest days on record. Normals are the 1991–2020 averages at Plevna, 23 km from Ismay; records cover 1910–2026.
The year at a glance
- Precipitation a year
- 15.6 in397 mm
- Snow a year
- 34 in87 cm
- Last spring freeze
- May 20
- First fall freeze
- Sep 21
- Heating degree days
- 8,073
- Cooling degree days
- 515
Freeze dates are medians (half of years earlier, half later). Degree days use a 65°F base; HVAC design temperatures here are −23°−31° (heating, 99%) and 99°37° (cooling, 1%).
Month by month
Ismay in January
Highs average 30°−1° and lows 6°−14°, with 0.48 in12 mm of precipitation and 6 in15 cm of snow in a typical January.
- Record high
- 66°19° (1921)
- Record low
- −52°−47° (1916)
- Heating degree days
- 1455
- Cooling degree days
- 0
Ismay in February
Highs average 33°1° and lows 10°−12°, with 0.5 in13 mm of precipitation and 6 in14 cm of snow in a typical February.
- Record high
- 70°21° (1921)
- Record low
- −45°−43° (1936)
- Heating degree days
- 1211
- Cooling degree days
- 0
Ismay in March
Highs average 45°7° and lows 20°−6°, with 0.7 in18 mm of precipitation and 5 in14 cm of snow in a typical March.
- Record high
- 81°27° (2015)
- Record low
- −32°−36° (1996)
- Heating degree days
- 998
- Cooling degree days
- 0
Ismay in April
Highs average 57°14° and lows 30°−1°, with 1.6 in39 mm of precipitation and 5 in12 cm of snow in a typical April.
- Record high
- 92°33° (1926)
- Record low
- −9°−23° (1997)
- Heating degree days
- 648
- Cooling degree days
- 0
Ismay in May
Highs average 67°19° and lows 41°5°, with 2.9 in74 mm of precipitation and 1.3 in3.3 cm of snow in a typical May.
- Record high
- 100°38° (1934)
- Record low
- 7°−14° (1954)
- Heating degree days
- 358
- Cooling degree days
- 9
Ismay in June
Highs average 77°25° and lows 50°10°, with 2.7 in67 mm of precipitation in a typical June.
- Record high
- 110°43° (1988)
- Record low
- 23°−5° (1919)
- Heating degree days
- 112
- Cooling degree days
- 64
Ismay in July
Highs average 86°30° and lows 56°13°, with 1.9 in47 mm of precipitation in a typical July.
- Record high
- 111°44° (1936)
- Record low
- 35°2° (1972)
- Heating degree days
- 20
- Cooling degree days
- 212
Ismay in August
Highs average 86°30° and lows 54°12°, with 1.4 in34 mm of precipitation in a typical August.
- Record high
- 110°43° (1949)
- Record low
- 27°−3° (1941)
- Heating degree days
- 37
- Cooling degree days
- 184
Ismay in September
Highs average 75°24° and lows 44°7°, with 1.5 in38 mm of precipitation and 0.1 in0.3 cm of snow in a typical September.
- Record high
- 105°41° (1978)
- Record low
- 12°−11° (1926)
- Heating degree days
- 206
- Cooling degree days
- 44
Ismay in OctoberThis month
Highs average 58°15° and lows 31°0°, with 1.2 in29 mm of precipitation and 2 in5.1 cm of snow in a typical October.
- Record high
- 94°34° (1953)
- Record low
- −16°−27° (1925)
- Heating degree days
- 631
- Cooling degree days
- 2
Ismay in November
Highs average 43°6° and lows 19°−7°, with 0.58 in15 mm of precipitation and 4 in10 cm of snow in a typical November.
- Record high
- 79°26° (1978)
- Record low
- −32°−36° (1985)
- Heating degree days
- 1018
- Cooling degree days
- 0
Ismay in December
Highs average 32°0° and lows 9°−13°, with 0.43 in11 mm of precipitation and 5 in13 cm of snow in a typical December.
- Record high
- 70°21° (2021)
- Record low
- −45°−43° (1989)
- Heating degree days
- 1379
- Cooling degree days
- 0