Last frost date in Helena, Montana
May 9
Average last frost in spring. In an early year (1 in 10) it's over by April 29; in a late year (1 in 10) it comes after May 25.
September 30
Average first frost in fall. 1 year in 10 it comes by September 17.
Source: NOAA U.S. Climate Normals 1991–2020, station Helena Rgnl AP (USW00024144), 2.8 miles from Helena, elevation 3,828 ft. NOAA National Centers for Environmental Information. These are long-term averages, not a forecast.
| Early year | Average | Late year | |
|---|---|---|---|
| Last frost in spring | Apr 29 | May 9 | May 25 |
| First frost in fall | Sept 17 | Sept 30 | Oct 11 |
Frost-free days in an average year: 142
| Chance in a year | Average last in spring | Average first in fall | |
|---|---|---|---|
| Light frost (36°F) | Every year | May 25 | Sept 19 |
| Frost (32°F) | Every year | May 9 | Sept 30 |
| Hard freeze (28°F) | Every year | Apr 29 | Oct 7 |
Nights at 32°F or colder in an average year: 170
What to plant now in Helena
- Spring planting calendar for an average last frost around May 10 Helena: May 9
- Fall planting calendar for an average first frost around September 30 Helena: September 30
Planting dates: USDA Home and Garden Bulletin No. 9 (1967), “Suburban and Farm Vegetable Gardens,” tables 4 and 5. How we match the table.
Nearby in Montana
- Butte-Silver Bow (balance) 57 mi · last frost June 13
- Belgrade 69 mi · last frost May 26
- Great Falls 71 mi · last frost May 6
- Bozeman 78 mi · last frost May 26
- Missoula 97 mi · last frost May 10
Updated