Zone 4a

Hardiness Zone 4a

USDA hardiness zone 4a has an average coldest winter night of -30 to -25 °F (-34 to -32 °C). On the 2023 map it covers ZIP codes in 15 states, mostly North Dakota, Minnesota and Wisconsin. Cities in zone 4a include Fargo, ND; Bismarck, ND; Grand Forks, ND.

Average coldest night

-30 to -25 °F

-34 to -32 °C

States with zone 4a

ZIP codes in zone 4a

814

Check your own zone

States in zone 4a

State	ZIP codes	Share of state
North Dakota	316	78%
Minnesota	200	21%
Wisconsin	73	8%
Montana	71	18%
Alaska	31	11%
New York	29	1%
Maine	26	5%
South Dakota	24	6%
Michigan	13	1%
Vermont	11	4%
Wyoming	10	5%
New Hampshire	5	2%
Colorado	2	<1%
Idaho	2	1%
Utah	1	<1%

Cities in zone 4a

Larger places where every ZIP code is zone 4a.

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 4a?

In zone 4a the coldest night of the year averages -30 to -25 °F (-34 to -32 °C). That is an average over 1991–2020, so a hard winter can go lower.

Which states have zone 4a?

Zone 4a is found in North Dakota, Minnesota, Wisconsin, Montana, Alaska, New York, Maine, South Dakota, Michigan, Vermont, Wyoming, New Hampshire, Colorado, Idaho and Utah.

What is the difference between zone 4a and 4b?

Zone 4b is 5 °F warmer than 4a. Zone 4a has winter lows of -30 to -25 °F, and zone 4b -25 to -20 °F. Plant labels often give only the number, which covers both halves.

What plants grow in zone 4a?

Plants labelled hardy to zone 4 or colder (a lower number) should survive a zone 4a 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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