Maryland climate

Maryland Plant Hardiness Zones

Maryland’s towns run from zone 6a to zone 8a: the average coldest winter night is 13.8°F at Crisfield and -8.6°F at Grantsville.

Hardiness zones in Maryland

In USDA’s colors, neighboring states washed out. Zones follow elevation, coasts and cities down to half a mile. Drawn by WeatherOverTime from the USDA-ARS and Oregon State University PRISM Climate Group 2023 GIS data; this is not the official USDA Plant Hardiness Zone Map.

Map of the 2023 plant hardiness zones across Maryland, from zone 5b to zone 8a, with the state’s border drawn.
  • 5b
  • 6a
  • 6b
  • 7a
  • 7b
  • 8a

Open the live map with plant hardiness zones

Towns by zone

Each town’s 1991-2020 average annual extreme minimum at its center, read from the map’s 800 m grid. Warmest zone first.

8a Zone 8a, 10 to 15°F 135 towns

7b Zone 7b, 5 to 10°F 409 towns

7a Zone 7a, 0 to 5°F 58 towns

6b Zone 6b, -5 to 0°F 5 towns

6a Zone 6a, -10 to -5°F 5 towns

Counties

At the county’s center; a county with hills or a coast spans several zones.

CountyZone at the centerAverage coldest night
Allegany County7a0.3°F
Anne Arundel County7b9.3°F
Baltimore County7b6.6°F
Calvert County8a11.2°F
Caroline County7b7°F
Carroll County7a3.7°F
Cecil County7b5.9°F
Charles County7b7°F
City of Baltimore8a11.2°F
Dorchester County8a11.2°F
Frederick County7b5.4°F
Garrett County6a-8.2°F
Harford County7b5.1°F
Howard County7b5.9°F
Kent County7b8.4°F
Montgomery County7b6.6°F
Prince George's County7b8.2°F
Queen Anne's County7b8.8°F
Saint Mary's County8a10.3°F
Somerset County8a12.8°F
Talbot County8a10.9°F
Washington County7a2.6°F
Wicomico County7b8.5°F
Worcester County7b8.1°F

The zones

A plant hardiness zone is set by the average of each winter’s single coldest temperature, 1991 to 2020: zones are 10°F apart and each half zone, a and b, 5°F. It says how cold a winter night usually gets, not the coldest it has ever been, and nothing about summer heat, rain or soil. Plant labels give the coldest zone a perennial survives in.

ZoneAverage coldest nightIn Celsius
6a-10 to -5°F-23.3 to -20.6°C
6b-5 to 0°F-20.6 to -17.8°C
7a0 to 5°F-17.8 to -15.0°C
7b5 to 10°F-15.0 to -12.2°C
8a10 to 15°F-12.2 to -9.4°C

Sources

Hardiness zones: USDA Plant Hardiness Zone Map, 2023, Agricultural Research Service, U.S. Department of Agriculture, from the GIS data of the PRISM Climate Group, Oregon State University, which may be freely reproduced and redistributed. Drawn by WeatherOverTime from the USDA-ARS and Oregon State University PRISM Climate Group 2023 GIS data; this is not the official USDA Plant Hardiness Zone Map.