Deconstruct SunHardiness Zone 1a: Temperature, States & Cities
In USDA zone 1a, the coldest night of a typical winter falls between −60 and −55 °F (−51.1 to −48.3 °C).
average annual extreme minimum
Where is zone 1a?
On the 2023 USDA map, zone 1a appears in Alaska.
Gardening in zone 1a
Pick perennials, shrubs and trees labeled for zone 1a or a lower number. Then match the light: every plant tag also lists full sun, part sun or shade, and that depends on the exact spot, not the zone.
Check your zone
Zone checked. Now measure the sun.
Deconstruct Sun shows how many hours of direct sun one exact spot gets, today and in every season. Free on iPhone.
Questions
What is the temperature range for zone 1a?
In zone 1a, the average coldest winter night is −60 to −55 °F (−51.1 to −48.3 °C). That is the average of each year’s lowest temperature from 1991 to 2020.
What is the difference between zone 1a and 1b?
Both are part of zone 1. The “a” half is 5 °F colder than the “b” half. Zone 1a averages −60 to −55 °F and zone 1b averages −55 to −50 °F.
Can I grow zone 1b plants in zone 1a?
A plant rated for a warmer zone may survive a mild winter, but one hard freeze can kill it. Choose plants rated for your zone or colder for permanent plantings, and treat warmer-zone plants as annuals or grow them in pots you can move.
This is not the official USDA Plant Hardiness Zone Map. Zones are derived from the official 2023 dataset, resampled to about 2 km.