Boulder, CO Frost Dates
The last spring frost in Boulder usually comes around May 6 and the first fall frost around October 5.
| Spring (last) | Fall (first) | |
|---|---|---|
| Frost, 32°F | May 6 | October 5 |
| Hard freeze, 28°F | April 27 | October 15 |
Growing season: about 151 days.
Frequently asked questions
When is the last frost in Boulder, CO?
The median date of the last spring frost (32°F) is May 6. In half of years the last frost comes earlier and in half it comes later, so waiting a week or two past May 6 lowers the risk for tender plants.
When is the first frost in Boulder?
The median date of the first fall frost (32°F) is October 5, and a hard freeze (28°F) usually follows around October 15.
How long is the growing season in Boulder?
About 151 days between the median last spring frost and first fall frost.
NOAA NCEI U.S. Climate Normals 1991-2020, station USC00050848. Median (50% probability) dates. Low spots and valleys can frost later in spring and earlier in fall than the station.