Arizona climate

Arizona Plant Hardiness Zones

Arizona’s towns run from zone 6a to zone 10a: the average coldest winter night is 34°F at Orange Grove Mobile Manor and -7.9°F at Flagstaff.

Hardiness zones in Arizona

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 Arizona, from zone 5b to zone 10a, with the state’s border drawn.
  • 5b
  • 6a
  • 6b
  • 7a
  • 7b
  • 8a
  • 8b
  • 9a
  • 9b
  • 10a

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.

10a Zone 10a, 30 to 35°F 25 towns

9b Zone 9b, 25 to 30°F 61 towns

9a Zone 9a, 20 to 25°F 56 towns

8b Zone 8b, 15 to 20°F 50 towns

8a Zone 8a, 10 to 15°F 16 towns

7b Zone 7b, 5 to 10°F 17 towns

7a Zone 7a, 0 to 5°F 30 towns

6b Zone 6b, -5 to 0°F 21 towns

6a Zone 6a, -10 to -5°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
Apache County6b-3.1°F
Cochise County8a14.2°F
Coconino County6a-8°F
Gila County9a20.9°F
Graham County8b15.9°F
Greenlee County8a14°F
La Paz County9a22.9°F
Maricopa County9b27.5°F
Mohave County8a13.1°F
Navajo County7a0.5°F
Pima County9b25°F
Pinal County9b25.2°F
Santa Cruz County8b17.4°F
Yavapai County7b7.8°F
Yuma County9b25.1°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
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
7b5 to 10°F-15.0 to -12.2°C
8a10 to 15°F-12.2 to -9.4°C
8b15 to 20°F-9.4 to -6.7°C
9a20 to 25°F-6.7 to -3.9°C
9b25 to 30°F-3.9 to -1.1°C
10a30 to 35°F-1.1 to 1.7°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.