Glossary /
Plant hardiness zone
A plant hardiness zone is a geographic band defined by the average annual extreme minimum temperature — the coldest night of a typical year, averaged over 30 years. The USDA's 2023 map divides the United States into 13 zones, each a 10°F band, split into 5°F half-zones labeled a and b. Zone 6b, for example, spans -5°F to 0°F. Perennials rated for your zone should survive your typical winter; vegetables are usually timed by frost dates instead. Find yours with our ZIP lookup.
The 13 zones (2023 map)
| Zone | Avg coldest night | US ZIPs |
|---|---|---|
| 1a | -60 to -55°F | 5 |
| 1b | -55 to -50°F | 11 |
| 2a | -50 to -45°F | 27 |
| 2b | -45 to -40°F | 17 |
| 3a | -40 to -35°F | 23 |
| 3b | -35 to -30°F | 230 |
| 4a | -30 to -25°F | 814 |
| 4b | -25 to -20°F | 1,284 |
| 5a | -20 to -15°F | 2,426 |
| 5b | -15 to -10°F | 2,880 |
| 6a | -10 to -5°F | 5,187 |
| 6b | -5 to 0°F | 5,271 |
| 7a | 0 to 5°F | 4,877 |
| 7b | 5 to 10°F | 3,855 |
| 8a | 10 to 15°F | 3,430 |
| 8b | 15 to 20°F | 3,379 |
| 9a | 20 to 25°F | 2,199 |
| 9b | 25 to 30°F | 2,085 |
| 10a | 30 to 35°F | 1,234 |
| 10b | 35 to 40°F | 752 |
| 11a | 40 to 45°F | 205 |
| 11b | 45 to 50°F | 16 |
| 12a | 50 to 55°F | 30 |
| 12b | 55 to 60°F | 137 |
| 13a | 60 to 65°F | 102 |
| 13b | 65 to 70°F | 26 |
See also: Last frost date · Growing season