Not every county offers a long growing season. In Alaska, the northern Great Plains, and high-elevation mountain counties, frost-free periods can be measured in weeks rather than months. For lawn owners in these counties, every warm day counts.
We identified the 25 counties with the shortest growing seasons — places where lawn care is a race against time and cold-hardy grass varieties are not optional but essential.
Counties with the Shortest Growing Seasons
Eagle County, CO has just 78 frost-free days per year. Lawns here must establish quickly and survive long, harsh winters.
| Rank | County | State | Frost-Free Days | Hardiness Zone | First Fall Frost |
|---|---|---|---|---|---|
| 1 | Eagle County | CO | 78 | 5b | 09/07 |
| 2 | Park County | CO | 85 | 5b | 09/09 |
| 3 | Teton County | ID | 86 | 5a | 09/09 |
| 4 | Silver Bow County | MT | 86 | 5a | 09/07 |
| 5 | Gunnison County | CO | 87 | 5a | 09/16 |
| 6 | Grand County | CO | 88 | 5a | 09/10 |
| 7 | Custer County | CO | 90 | 5b | 09/09 |
| 8 | Camas County | ID | 90 | 6a | 09/14 |
| 9 | Boise County | ID | 91 | 6b | 09/05 |
| 10 | Meagher County | MT | 92 | 4b | 09/11 |
| 11 | Harney County | OR | 92 | 6b | 09/11 |
| 12 | Valley County | ID | 93 | 5a | 09/11 |
| 13 | Jefferson County | MT | 93 | 5a | 09/08 |
| 14 | Hinsdale County | CO | 94 | 5a | 09/17 |
| 15 | Wallowa County | OR | 94 | 6b | 09/09 |
| 16 | Routt County | CO | 95 | 5a | 09/12 |
| 17 | Bear Lake County | ID | 96 | 5a | 09/21 |
| 18 | Iron County | MI | 96 | 4a | 09/10 |
| 19 | Glacier County | MT | 97 | 4b | 09/08 |
| 20 | Lake County | OR | 99 | 6b | 09/17 |
| 21 | Daniels County | MT | 101 | 3b | 09/06 |
| 22 | Alamosa County | CO | 103 | 5a | 09/17 |
| 23 | Custer County | ID | 103 | 5b | 09/25 |
| 24 | Elko County | NV | 103 | 5b | 09/18 |
| 25 | Summit County | UT | 103 | 5b | 09/18 |
Lawn Strategies for Short Seasons
- Choose cold-hardy grasses like Kentucky bluegrass and fine fescue that germinate quickly in cool soil.
- Seed as early as possible in spring to maximize the short establishment window.
- Consider sod installation rather than seeding to bypass the germination period entirely.
- Use winterizer fertilizer in late fall to strengthen roots before dormancy.
Methodology
Counties ranked by shortest growing season length (days between last spring and first fall frost at 32°F). Data 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.