New USDA Plant Hardiness Zone Map

Published On: December 21st, 2023

USDA Plant Hardiness Zone Map 2023

In November of 2023 the U.S. Department of Agriculture released an updated version of its Plant Hardiness Zone Map (PHZM). This zone map helps gardeners to determine which plants are most likely to thrive in their area. The last version of the map was released in 2012 and the 2023 version has bumped most areas up by one quarter zone, indicating an increase of approximately 2.5 degrees in the average annual extreme minimum temperature.

The map is divided into 13 zones, with 1 being the coldest (Alaska) and 13 being the warmest (Hawaii). Each zone represents a 10-degree range, and within each 10-degree zone there is a further breakdown to five-degree half-zones, classified as “a” and “b”. The “a” section of the zone is the colder part of the zone and “b” the warmer. Cedarburg, Wisconsin is currently classified as Zone 5b (-15°F to -10°F  average minimum temperature). Wisconsin zones range from 5b in southeastern Wisconsin to 4a in northwestern Wisconsin.

The 2023 Plant Hardiness Zone Map is based on 30-year averages of the lowest winter temperatures at specific locations, based on data collected from 13,412 weather stations across the United States. The designations do not reflect the coldest it has ever been at a specific location, but rather the average lowest winter temperature for the location over a specified time.

Click HERE for an interactive version of the new map.

By Zannah Crowe