LawnByCounty

Counties with the Fewest Extreme Heat Days

Published May 2, 2026

Extreme heat days — when temperatures exceed 90°F — stress grass, increase water demand, and can push cool-season lawns into dormancy or death. Counties with few extreme heat days enjoy milder summers where lawns stay greener with less water and fewer interventions.

We identified the 25 counties with the fewest extreme heat days, concentrated in the Pacific Coast, mountain West, and northern tier of the country.

Counties with the Fewest Extreme Heat Days

Clear Creek County, CO averages just 0 days above 90°F per year. Cool-season grasses thrive in these conditions.

RankCountyStateHeat Days/YearJuly Avg (°F)Hardiness Zone
1Clear Creek CountyCO060.155b
2Eagle CountyCO059.25b
3Gilpin CountyCO060.155b
4Hinsdale CountyCO060.355a
5Lake CountyCO055.85a
6San Juan CountyCO056.55a
7Hamilton CountyNY064.34b
8Del Norte CountyCA0.0666666666666666758.3333333333333369b
9Mineral CountyCO0.0750000000000000159.1750000000000045a
10Park CountyCO0.159.5199999999999965b
11Teller CountyCO0.161.255b
12Wyoming CountyNY0.167.15b
13Nantucket CountyMA0.2697b
14Madison CountyNY0.367.35b
15Watauga CountyNC0.368.47a
16Island CountyWA0.361.458b
17San Juan CountyWA0.361.459a
18Forest CountyWI0.364.24b
19Jackson CountyCO0.333333333333333357.6333333333333264b
20Summit CountyCO0.3559.15a
21Schoolcraft CountyMI0.464.85a
22Avery CountyNC0.467.26b
23Greene CountyVA0.467.17b
24Madison CountyVA0.467.17a
25Grand CountyCO0.4859.859999999999995a

Methodology

Counties ranked by fewest extreme heat days (days above 90°F) from NOAA 1991-2020 climate normals.

Data sourced from USDA Plant Hardiness Zone Map (2023), NOAA National Centers for Environmental Information (1991-2020 Climate Normals), and US Drought Monitor. All figures represent long-term averages and may differ from individual-year observations.

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