Last frost date in Longmont, Colorado
May 7
Average last frost in spring. In an early year (1 in 10) it's over by April 24; in a late year (1 in 10) it comes after May 22.
October 5
Average first frost in fall. 1 year in 10 it comes by September 23.
Source: NOAA U.S. Climate Normals 1991–2020, station Longmont 2 Ese (USC00055116), 1.2 miles from Longmont, elevation 4,950 ft. NOAA National Centers for Environmental Information. These are long-term averages, not a forecast.
This station is also the nearest one for Berthoud, Erie, Firestone and Frederick, so their frost dates are the same as Longmont's.
| Early year | Average | Late year | |
|---|---|---|---|
| Last frost in spring | Apr 24 | May 7 | May 22 |
| First frost in fall | Sept 23 | Oct 5 | Oct 16 |
Frost-free days in an average year: 151
| Chance in a year | Average last in spring | Average first in fall | |
|---|---|---|---|
| Light frost (36°F) | Every year | May 18 | Sept 28 |
| Frost (32°F) | Every year | May 7 | Oct 5 |
| Hard freeze (28°F) | Every year | Apr 28 | Oct 12 |
Nights at 32°F or colder in an average year: 178
What to plant now in Longmont
- Spring planting calendar for an average last frost around May 10 Longmont: May 7
- Fall planting calendar for an average first frost around September 30 Longmont: October 5
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 Colorado
Updated