🌡️ USDA Hardiness Zone Reference

Select a USDA Plant Hardiness Zone to see its average annual extreme minimum temperature range — the standard used to determine which perennial plants can survive winter in a given area.

USDA Hardiness Zone

How the bands are laid out

Every zone is a 10°F band of average annual extreme minimum temperature, from zone 1 at −60°F up to zone 13 topping out at 70°F:

zone n low = −60 + 10 × (n − 1) °F      °C = (°F − 32) × 5/9

Zone 6 is therefore −10 to 0°F, or about −23 to −18°C, and zone 9 is 20 to 30°F (−7 to −1°C). The picker offers zones 3 to 11; the table beneath lists all thirteen. The official map also splits each zone into 5°F halves, 6a being −10 to −5°F and 6b −5 to 0°F, which are not shown here.

What the number actually describes

An average, not a worst case. It is the mean of the coldest night in each year, so roughly half of winters dip below your zone's floor. A plant rated exactly to your zone is on the edge, not safe.
The map was revised in November 2023, using 1991–2020 normals in place of the 2012 edition's 1976–2005 data. Around half of the country moved half a zone warmer, mostly a change of dataset and method, not licence to plant something tender.
Winter cold only. Zones say nothing about summer heat, humidity, rainfall, soil or growing-season length, and nothing about frost dates: two places in one zone can differ by a month in spring.

Your own plot may not match its map colour. A south wall or city centre can hold a zone warmer; a frost hollow or exposed ridge runs colder. Snow cover, drainage and how hard the ground freezes cost as many plants as air temperature does.

Frequently asked questions

What temperature is zone 7?

An average annual extreme minimum of 0 to 10°F, which is −18 to −12°C. Zone 7a covers 0 to 5°F and 7b covers 5 to 10°F.

How do I find my hardiness zone?

Enter your postcode on the USDA's Plant Hardiness Zone Map site, which resolves to about half-mile squares. Older labels and books may still quote the 2012 map, so check the edition.

Can I grow a plant rated one zone warmer than mine?

Sometimes, in a sheltered spot with good drainage and winter mulch. Expect to lose it in a hard winter, so treat it as an experiment, not the hedge you are relying on.