Zone 6a

Hardiness Zone 6a

USDA hardiness zone 6a has an average coldest winter night of -10 to -5 °F (-23 to -21 °C). On the 2023 map it covers ZIP codes in 30 states, mostly Illinois, Michigan and Indiana. Cities in zone 6a include Denver, CO; Albany, NY; Fort Wayne, IN.

Average coldest night

-10 to -5 °F

-23 to -21 °C

States with zone 6a

ZIP codes in zone 6a

5,187

Check your own zone

States in zone 6a

State	ZIP codes	Share of state
Illinois	646	42%
Michigan	640	55%
Indiana	567	61%
Ohio	544	39%
Pennsylvania	510	24%
New York	499	23%
Colorado	274	44%
Missouri	216	19%
Nebraska	206	34%
Kansas	178	24%
Massachusetts	154	23%
New Hampshire	119	43%
Maine	109	23%
Utah	108	32%
New Mexico	64	15%
West Virginia	57	7%
Idaho	52	17%
Connecticut	51	12%
Wisconsin	47	5%
Montana	30	8%
Iowa	29	3%
Oregon	27	6%
Washington	17	2%
Nevada	11	4%
Maryland	9	2%
California	7	<1%
Arizona	6	1%
Alaska	4	1%
Virginia	4	<1%
Vermont	2	1%

Cities in zone 6a

Larger places where every ZIP code is zone 6a.

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 6a?

In zone 6a the coldest night of the year averages -10 to -5 °F (-23 to -21 °C). That is an average over 1991–2020, so a hard winter can go lower.

Which states have zone 6a?

Zone 6a is found in Illinois, Michigan, Indiana, Ohio, Pennsylvania, New York, Colorado, Missouri, Nebraska, Kansas, Massachusetts, New Hampshire, Maine, Utah, New Mexico, West Virginia, Idaho, Connecticut, Wisconsin, Montana, Iowa, Oregon, Washington, Nevada, Maryland, California, Arizona, Alaska, Virginia and Vermont.

What is the difference between zone 6a and 6b?

Zone 6b is 5 °F warmer than 6a. Zone 6a has winter lows of -10 to -5 °F, and zone 6b -5 to 0 °F. Plant labels often give only the number, which covers both halves.

What plants grow in zone 6a?

Plants labelled hardy to zone 6 or colder (a lower number) should survive a zone 6a 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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