US Hardiness Zone Insights
National analysis of USDA plant hardiness zones and minimum temperatures across all 3,144 US counties. Data from USDA PHZM 2023.
National Avg Min Temp
-1°F
Zones Represented
17
Counties Analyzed
3,076
Key Findings
USDA hardiness zones span from 3a (minimum -40°F) to 11b (minimum 45°F) across US counties.Florida is the warmest state with an average minimum of 25°F, while North Dakota is the coldest at -30°F.
The national average minimum temperature is -1°F, but this average obscures enormous local variation driven by elevation, latitude, and proximity to large bodies of water. These minimums are the primary constraint on perennial plant and tree selection.
Hardiness Zone Distribution
Number of counties in each USDA plant hardiness zone. The distribution shows which zones cover the most US counties.
State Minimum Temperature Rankings
Average hardiness minimum temperature by state. Warmer states allow a wider range of perennial plants, while colder states are limited to hardier species.
Warmest States
Coldest States
Warmest Counties
The 10 counties with the highest hardiness minimum temperatures. These counties can support the widest variety of tropical and subtropical plants.