Frost dates in Boulder, CO
The average last spring frost in Boulder is around May 5 and the first fall frost is around October 8. That gives Boulder an average growing season of about 156 days.
Last spring frost
| Early (10% chance after) | April 21 |
|---|---|
| Average (50%) | May 5 |
| Late (90%) | May 21 |
First fall frost
| Early (10%) | September 20 |
|---|---|
| Average (50%) | October 8 |
| Late (90% chance before) | October 24 |