Colorado climate

Colorado Plant Hardiness Zones

Colorado’s towns run from zone 4a to zone 7a: the average coldest winter night is 3.9°F at Palisade and -29.4°F at Fraser.

Hardiness zones in Colorado

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 Colorado, from zone 3b to zone 7a, with the state’s border drawn.
  • 3b
  • 4a
  • 4b
  • 5a
  • 5b
  • 6a
  • 6b
  • 7a

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.

7a Zone 7a, 0 to 5°F 7 towns

6b Zone 6b, -5 to 0°F 18 towns

6a Zone 6a, -10 to -5°F 110 towns

5b Zone 5b, -15 to -10°F 105 towns

5a Zone 5a, -20 to -15°F 32 towns

4b Zone 4b, -25 to -20°F 7 towns

4a Zone 4a, -30 to -25°F 8 towns

Counties

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

CountyZone at the centerAverage coldest night
Adams County5b-11.6°F
Alamosa County5a-20°F
Arapahoe County5b-10.1°F
Archuleta County6a-9.9°F
Baca County6b-4.2°F
Bent County6a-7.5°F
Boulder County6a-9.5°F
Broomfield County6a-7.9°F
Chaffee County6b-4.1°F
Cheyenne County6a-9.5°F
Clear Creek County5b-12.5°F
Conejos County6a-9.7°F
Costilla County5b-13.7°F
Crowley County5b-10.3°F
Custer County5b-13.9°F
Delta County7a0.9°F
Denver County6a-8.1°F
Dolores County6a-7°F
Douglas County5b-11.5°F
Eagle County6a-8.1°F
El Paso County6a-9.2°F
Elbert County5b-12.7°F
Fremont County6a-8.8°F
Garfield County6a-8.3°F
Gilpin County5b-14.8°F
Grand County4b-20.6°F
Gunnison County5b-11.4°F
Hinsdale County5a-16.1°F
Huerfano County6a-7.3°F
Jackson County4b-24.6°F
Jefferson County5b-11.8°F
Kiowa County6a-8.3°F
Kit Carson County6a-8.9°F
La Plata County6b-2.5°F
Lake County5a-18.3°F
Larimer County5b-12.2°F
Las Animas County6a-7.7°F
Lincoln County5b-12.3°F
Logan County5b-13.3°F
Mesa County7a1°F
Mineral County5b-14.2°F
Moffat County6a-9.5°F
Montezuma County6a-5.3°F
Montrose County6a-8.5°F
Morgan County5b-14.8°F
Otero County6a-9.5°F
Ouray County5b-14.5°F
Park County4b-21.7°F
Phillips County5b-12.6°F
Pitkin County5b-10.4°F
Prowers County6a-7.7°F
Pueblo County6a-8.3°F
Rio Blanco County5b-14.4°F
Rio Grande County5b-12°F
Routt County4b-21.5°F
Saguache County5b-10.7°F
San Juan County5a-15.9°F
San Miguel County5b-11°F
Sedgwick County5b-12.6°F
Summit County5a-19.2°F
Teller County5b-14.7°F
Washington County5b-12°F
Weld County5a-16.8°F
Yuma County5b-11.2°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
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
7a0 to 5°F-17.8 to -15.0°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.