USDA plant hardiness zones
The 2023 USDA map sorts places into half-zones from 1a to 13b, each 5°F wide, by the coldest night of the winter averaged over 1991–2020; 25 of them include at least one ZIP code. Pick a zone to see its range, the cities we cover in it and how many of the 40,326 ZIP codes on the map it includes. Your own ZIP’s zone shows next to its frost dates on the home page.
- Zone 1a−60 to −55°F (−51.1 to −48.3°C) · 5 ZIP codes
- Zone 1b−55 to −50°F (−48.3 to −45.6°C) · 11 ZIP codes
- Zone 2a−50 to −45°F (−45.6 to −42.8°C) · 27 ZIP codes
- Zone 2b−45 to −40°F (−42.8 to −40.0°C) · 17 ZIP codes
- Zone 3a−40 to −35°F (−40.0 to −37.2°C) · 23 ZIP codes
- Zone 3b−35 to −30°F (−37.2 to −34.4°C) · 230 ZIP codes
- Zone 4a−30 to −25°F (−34.4 to −31.7°C) · 814 ZIP codes
- Zone 4b−25 to −20°F (−31.7 to −28.9°C) · 1,284 ZIP codes
- Zone 5a−20 to −15°F (−28.9 to −26.1°C) · 2,426 ZIP codes
- Zone 5b−15 to −10°F (−26.1 to −23.3°C) · 2,880 ZIP codes
- Zone 6a−10 to −5°F (−23.3 to −20.6°C) · 5,187 ZIP codes
- Zone 6b−5 to 0°F (−20.6 to −17.8°C) · 5,271 ZIP codes
- Zone 7a0 to 5°F (−17.8 to −15.0°C) · 4,877 ZIP codes
- Zone 7b5 to 10°F (−15.0 to −12.2°C) · 3,855 ZIP codes
- Zone 8a10 to 15°F (−12.2 to −9.4°C) · 3,430 ZIP codes
- Zone 8b15 to 20°F (−9.4 to −6.7°C) · 3,379 ZIP codes
- Zone 9a20 to 25°F (−6.7 to −3.9°C) · 2,199 ZIP codes
- Zone 9b25 to 30°F (−3.9 to −1.1°C) · 2,085 ZIP codes
- Zone 10a30 to 35°F (−1.1 to 1.7°C) · 1,234 ZIP codes
- Zone 10b35 to 40°F (1.7 to 4.4°C) · 752 ZIP codes
- Zone 11a40 to 45°F (4.4 to 7.2°C) · 205 ZIP codes
- Zone 11b45 to 50°F (7.2 to 10.0°C) · 14 ZIP codes
- Zone 12a50 to 55°F (10.0 to 12.8°C) · 24 ZIP codes
- Zone 12b55 to 60°F (12.8 to 15.6°C) · 95 ZIP codes
- Zone 13a60 to 65°F (15.6 to 18.3°C) · 2 ZIP codes
What zones do and don’t tell you
What a zone tells you
How cold winter nights usually get: the lowest temperature of each winter, averaged over 1991–2020. Gardeners and nurseries use it to judge whether a perennial, shrub or tree is likely to survive the winter. It is an average, so some winters still get colder.
What it doesn’t
When to plant. Two gardens in the same zone can have their last spring frost weeks apart, because frost dates depend on elevation, nearby water and how fast spring warms up, not on the coldest night of winter. The zone says nothing about summer heat either.
For planting dates
Vegetables, herbs and annual flowers are timed from frost dates. We give them by ZIP code, from the nearest NOAA weather station. Find your frost dates
Hardiness zones: 2023 USDA Plant Hardiness Zone Map, PRISM Group, Oregon State University, https://prism.oregonstate.edu, accessed 9 Nov 2026.