Colorado frost dates: A
| City | Last frost | First frost | Season | Zone |
|---|---|---|---|---|
| Agate | May 12 | Oct 2 | 143 d | 5b |
| Aguilar | May 6 | Oct 4 | 151 d | 6a |
| Akron | May 6 | Oct 8 | 155 d | 5b |
| Alamosa | May 30 | Sep 17 | 110 d | 4b |
| Allenspark | Jun 14 | Sep 12 | 90 d | 5b |
| Alma | Jun 16 | Sep 9 | 85 d | 5a |
| Almont | Jun 20 | Sep 8 | 80 d | 5a |
| Amherst | May 11 | Oct 3 | 145 d | 5b |
| Anton | May 12 | Oct 4 | 145 d | 5b |
| Antonito | May 28 | Sep 21 | 116 d | 5b |
| Arapahoe | May 1 | Oct 14 | 166 d | 6a |
| Arboles | May 23 | Sep 29 | 129 d | 6b |
| Arlington | May 3 | Oct 7 | 157 d | 5b |
| Arriba | May 5 | Oct 8 | 156 d | 5b |
| Arvada | May 5 | Oct 5 | 153 d | 6a |
| Aspen | May 31 | Sep 23 | 115 d | 5a |
| Atwood | Apr 30 | Oct 9 | 162 d | 5b |
| Ault | May 2 | Oct 8 | 159 d | 5a |
| Aurora | May 7 | Oct 8 | 154 d | 6a |
| Aurora (Arapahoe) | May 5 | Oct 9 | 157 d | 6a |
| Austin | May 1 | Oct 7 | 159 d | 6b |
| Avon | Jun 21 | Sep 7 | 78 d | 6a |
| Avondale | Apr 30 | Oct 9 | 162 d | 6a |