Zone 1a

Hardiness Zone 1a

USDA hardiness zone 1a has an average coldest winter night of -60 to -55 °F (-51 to -48 °C). On the 2023 map it is found only in Alaska. Cities in zone 1a include Allakaket, AK; Beaver, AK; Chalkyitsik, AK.

Average coldest night

-60 to -55 °F

-51 to -48 °C

States with zone 1a

ZIP codes in zone 1a

Check your own zone

States in zone 1a

State	ZIP codes	Share of state
Alaska	5	2%

Cities in zone 1a

Larger places where every ZIP code is zone 1a.

Zones: 2023 USDA Plant Hardiness Zone Map ZIP code data, USDA Agricultural Research Service and the PRISM Climate Group, Oregon State University (official map). Place names: GeoNames (CC BY 4.0). Each ZIP code gets one zone, but a ZIP code can cross a zone line, and hills, valleys and towns can be warmer or colder than the zone shown.

About the Hardiness Zone Map

The Hardiness Zone Map finds your USDA plant hardiness zone, also called your planting or growing zone, from your ZIP code. Zones are based on the average coldest winter night of the year: each zone is 10 °F wide and split into a and b halves of 5 °F, from zone 1a in Alaska to 13b in Puerto Rico. Plant labels and seed packets give the coldest zone a plant can survive, so knowing your zone tells you which perennials, shrubs and trees can stay outside all winter. Zones come from the official 2023 USDA map ZIP code data for all 50 states, Washington DC and Puerto Rico.

How to use it

1 Enter your 5-digit ZIP code and press Find my zone.
2 Read your zone and the average coldest winter temperature it stands for.
3 Open your state to see its zones and the zone of every city.
4 Choose plants rated for your zone number or a colder (lower) one.

Frequently asked questions

What is the lowest temperature in zone 1a?

In zone 1a the coldest night of the year averages -60 to -55 °F (-51 to -48 °C). That is an average over 1991–2020, so a hard winter can go lower.

Which states have zone 1a?

Zone 1a is found in Alaska.

What is the difference between zone 1a and 1b?

Zone 1b is 5 °F warmer than 1a. Zone 1a has winter lows of -60 to -55 °F, and zone 1b -55 to -50 °F. Plant labels often give only the number, which covers both halves.

What plants grow in zone 1a?

Plants labelled hardy to zone 1 or colder (a lower number) should survive a zone 1a winter. Plants rated only for warmer zones may be damaged by frost unless grown in pots and brought in, or given shelter.

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