Free tool

USDA Hardiness Zone Lookup

Your hardiness zone tells you which perennials, shrubs, and trees can survive your winters. Enter a ZIP code to get your zone from the current 2023 USDA map.

Data: 2023 USDA ARS / PRISM Plant Hardiness Zone Map via the open PHZM API. Near a zone boundary? Confirm on the official USDA map.

How to read a hardiness zone

USDA zones are based on the average coldest night of the year, the "average annual extreme minimum temperature." Each numbered zone spans 10°F, and the "a" and "b" halves split it into 5°F bands. Zone 6a averages a coldest night of −10 to −5°F; zone 6b, −5 to 0°F.

The 2023 map uses 1991–2020 weather data, so many locations moved half a zone warmer than on the 2012 map. A plant labeled "zones 4–8" should survive a typical winter anywhere from zone 4 to zone 8.

Zones only measure cold. In the arid West, summer heat, rainfall, soil, and elevation matter as much, which is why our city pages add frost dates and precipitation from NOAA climate normals.

USDA zones common in the western U.S.
Zone	Average coldest night	Example city (sampled ZIP)
5a	−20 to −15°F	Billings
5b	−15 to −10°F	Cheyenne
6a	−10 to −5°F	Denver
6b	−5 to 0°F	Bend
7a	0 to 5°F	Boise
7b	5 to 10°F	Albuquerque
8b	15 to 20°F	El Paso
9a	20 to 25°F	Austin
9b	25 to 30°F	Sacramento
10b	35 to 40°F	Los Angeles

More detail: Understanding USDA hardiness zones.

Planting zones for western cities

Zone, frost dates, rainfall, and a starter plant list for each city.