Last frost date in Boulder, Colorado
May 6
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 18.
October 5
Average first frost in fall. 1 year in 10 it comes by September 21.
Source: NOAA U.S. Climate Normals 1991–2020, station Boulder (USC00050848), 2.4 miles from Boulder, elevation 5,484 ft. NOAA National Centers for Environmental Information. These are long-term averages, not a forecast.
This station is also the nearest one for Louisville and Superior, so their frost dates are the same as Boulder's.
| Early year | Average | Late year | |
|---|---|---|---|
| Last frost in spring | Apr 24 | May 6 | May 18 |
| First frost in fall | Sept 21 | Oct 5 | Oct 18 |
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 17 | Sept 28 |
| Frost (32°F) | Every year | May 6 | Oct 5 |
| Hard freeze (28°F) | Every year | Apr 27 | Oct 15 |
Nights at 32°F or colder in an average year: 138
What to plant now in Boulder
- Spring planting calendar for an average last frost around May 10 Boulder: May 6
- Fall planting calendar for an average first frost around September 30 Boulder: 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
- Longmont 13 mi · last frost May 7
- Arvada 14 mi · last frost May 5
- Thornton 18 mi · last frost May 2
- Lakewood 24 mi · last frost May 3
- Commerce City 26 mi · last frost May 3
Updated