Montana climate

Montana Plant Hardiness Zones

Montana’s towns run from zone 3b to zone 6b: the average coldest winter night is -3.5°F at Troy and -33.6°F at West Yellowstone.

Hardiness zones in Montana

In USDA’s colors, neighboring states washed out. Zones follow elevation, coasts and cities down to half a mile. Drawn by WeatherOverTime from the USDA-ARS and Oregon State University PRISM Climate Group 2023 GIS data; this is not the official USDA Plant Hardiness Zone Map.

Map of the 2023 plant hardiness zones across Montana, from zone 3a to zone 6b, with the state’s border drawn.
  • 3a
  • 3b
  • 4a
  • 4b
  • 5a
  • 5b
  • 6a
  • 6b

Open the live map with plant hardiness zones

Towns by zone

Each town’s 1991-2020 average annual extreme minimum at its center, read from the map’s 800 m grid. Warmest zone first.

6b Zone 6b, -5 to 0°F 2 towns

6a Zone 6a, -10 to -5°F 15 towns

5b Zone 5b, -15 to -10°F 24 towns

5a Zone 5a, -20 to -15°F 32 towns

4b Zone 4b, -25 to -20°F 46 towns

4a Zone 4a, -30 to -25°F 29 towns

3b Zone 3b, -35 to -30°F 9 towns

Counties

At the county’s center; a county with hills or a coast spans several zones.

CountyZone at the centerAverage coldest night
Beaverhead County5a-19.7°F
Big Horn County4b-21.8°F
Blaine County4a-28.4°F
Broadwater County4b-21.5°F
Carbon County5a-19.8°F
Carter County4b-24.6°F
Cascade County4b-23.5°F
Chouteau County4a-27.3°F
Custer County4b-23.8°F
Daniels County3b-31.7°F
Dawson County4a-25.2°F
Deer Lodge County5a-17.5°F
Fallon County4b-24.8°F
Fergus County4b-21.2°F
Flathead County5b-13.1°F
Gallatin County5a-18°F
Garfield County4a-25.7°F
Glacier County4a-26.5°F
Golden Valley County4b-21.8°F
Granite County5b-13.7°F
Hill County4a-30°F
Jefferson County5a-18.7°F
Judith Basin County4b-24.3°F
Lake County6a-10°F
Lewis and Clark County4b-24.7°F
Liberty County4a-29.4°F
Lincoln County6a-7.9°F
Madison County5a-17.8°F
McCone County4a-26.1°F
Meagher County4b-24.2°F
Mineral County6a-7.2°F
Missoula County5b-12.6°F
Musselshell County4b-22.4°F
Park County5a-17.7°F
Petroleum County4b-23.6°F
Phillips County4a-27.3°F
Pondera County4b-24.7°F
Powder River County4b-22.9°F
Powell County4b-24.9°F
Prairie County4a-27.1°F
Ravalli County6a-7.1°F
Richland County4a-25.7°F
Roosevelt County4a-29.7°F
Rosebud County4b-23.6°F
Sanders County6a-6.8°F
Sheridan County3b-31.8°F
Silver Bow County4a-27.7°F
Stillwater County5a-19.5°F
Sweet Grass County5a-19.3°F
Teton County4b-24.4°F
Toole County4a-28.5°F
Treasure County4b-22.2°F
Valley County4a-28.4°F
Wheatland County4b-23.6°F
Wibaux County4a-25.5°F
Yellowstone County4b-22.7°F

The zones

A plant hardiness zone is set by the average of each winter’s single coldest temperature, 1991 to 2020: zones are 10°F apart and each half zone, a and b, 5°F. It says how cold a winter night usually gets, not the coldest it has ever been, and nothing about summer heat, rain or soil. Plant labels give the coldest zone a perennial survives in.

ZoneAverage coldest nightIn Celsius
3b-35 to -30°F-37.2 to -34.4°C
4a-30 to -25°F-34.4 to -31.7°C
4b-25 to -20°F-31.7 to -28.9°C
5a-20 to -15°F-28.9 to -26.1°C
5b-15 to -10°F-26.1 to -23.3°C
6a-10 to -5°F-23.3 to -20.6°C
6b-5 to 0°F-20.6 to -17.8°C

Sources

Hardiness zones: USDA Plant Hardiness Zone Map, 2023, Agricultural Research Service, U.S. Department of Agriculture, from the GIS data of the PRISM Climate Group, Oregon State University, which may be freely reproduced and redistributed. Drawn by WeatherOverTime from the USDA-ARS and Oregon State University PRISM Climate Group 2023 GIS data; this is not the official USDA Plant Hardiness Zone Map.