Wisconsin climate

Wisconsin Plant Hardiness Zones

Wisconsin’s towns run from zone 4a to zone 6a: the average coldest winter night is -7.7°F at Milwaukee and -28.5°F at Minong.

Hardiness zones in Wisconsin

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

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.

6a Zone 6a, -10 to -5°F 24 towns

5b Zone 5b, -15 to -10°F 197 towns

5a Zone 5a, -20 to -15°F 185 towns

4b Zone 4b, -25 to -20°F 147 towns

4a Zone 4a, -30 to -25°F 21 towns

Counties

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

CountyZone at the centerAverage coldest night
Adams County4b-21.5°F
Ashland County5a-20°F
Barron County4b-24°F
Bayfield County4a-26°F
Brown County5b-14°F
Buffalo County4b-20.6°F
Burnett County4a-25.3°F
Calumet County5b-14.2°F
Chippewa County4b-22.8°F
Clark County4b-23.2°F
Columbia County5a-16.7°F
Crawford County5a-18.7°F
Dane County5b-14.9°F
Dodge County5a-16°F
Door County5b-13.1°F
Douglas County4a-27.6°F
Dunn County4b-20.7°F
Eau Claire County4b-22.7°F
Florence County4b-23.7°F
Fond du Lac County5b-14.5°F
Forest County4b-22.9°F
Grant County5a-17.7°F
Green County5a-15.3°F
Green Lake County5a-16.7°F
Iowa County5a-16.1°F
Iron County4a-27.5°F
Jackson County4b-22.9°F
Jefferson County5b-14.1°F
Juneau County4b-21.4°F
Kenosha County6a-9.5°F
Kewaunee County5b-11.3°F
La Crosse County5a-18.9°F
Lafayette County5a-18.3°F
Langlade County4b-23°F
Lincoln County4b-25°F
Manitowoc County5b-11.3°F
Marathon County4b-20.4°F
Marinette County4b-20.3°F
Marquette County5a-18.8°F
Menominee County5a-19.9°F
Milwaukee County6a-7.9°F
Monroe County4b-22°F
Oconto County5a-19.5°F
Oneida County4b-24.7°F
Outagamie County5a-15.4°F
Ozaukee County5b-10.6°F
Pepin County4b-21.8°F
Pierce County4b-22°F
Polk County4b-23.6°F
Portage County5a-19.7°F
Price County4a-26.1°F
Racine County6a-9.2°F
Richland County4b-20.7°F
Rock County5b-13.8°F
Rusk County4a-25.2°F
Saint Croix County4b-23.1°F
Sauk County5a-15.6°F
Sawyer County4a-28.8°F
Shawano County5a-18.5°F
Sheboygan County5b-11.2°F
Taylor County4a-26.3°F
Trempealeau County4b-24°F
Vernon County5a-19.5°F
Vilas County4b-24.3°F
Walworth County5b-12.4°F
Washburn County4a-26.5°F
Washington County5a-16.2°F
Waukesha County5b-13.9°F
Waupaca County5a-16.6°F
Waushara County4b-20.2°F
Winnebago County5b-14.1°F
Wood County4b-20.7°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
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

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.