| City | Population | Last spring frost | First fall frost | Growing season | Zone |
|---|---|---|---|---|---|
| Denver | 740,613 | May 4 | Oct 8 | 156 days | 6a |
| Colorado Springs | 494,743 | May 3 | Oct 8 | 158 days | 6a |
| Aurora | 410,053 | May 7 | Oct 8 | 152 days | 6a |
| Fort Collins | 171,500 | May 2 | Oct 7 | 157 days | 5b |
| Lakewood | 156,927 | May 3 | Oct 7 | 155 days | 6a |
| Thornton | 147,766 | May 2 | Oct 11 | 160 days | 6a |
| Arvada | 122,901 | May 5 | Oct 5 | 151 days | 6a |
| Westminster | 116,182 | May 2 | Oct 11 | 160 days | 6a |
| Greeley | 115,073 | May 2 | Oct 8 | 159 days | 5b |
| Pueblo | 110,404 | Apr 30 | Oct 9 | 162 days | 6a |
| Centennial | 108,658 | May 5 | Oct 8 | 154 days | 6a |
| Boulder | 105,689 | May 6 | Oct 5 | 151 days | 6a |
| Longmont | 100,109 | May 7 | Oct 5 | 151 days | 5b |
| Castle Rock | 83,815 | May 9 | Oct 2 | 143 days | 5b |
| Loveland | 81,387 | May 10 | Oct 1 | 142 days | 5b |
| Broomfield | 79,174 | May 2 | Oct 11 | 160 days | 6a |
| Commerce City | 72,345 | May 3 | Oct 7 | 155 days | 6a |
| Grand Junction | 71,827 | Apr 14 | Oct 23 | 190 days | 7a |
| Parker | 65,985 | May 9 | Oct 3 | 145 days | 5b |
| Littleton | 46,246 | May 2 | Oct 11 | 160 days | 6a |
| Brighton | 45,395 | May 3 | Oct 7 | 155 days | 5b |
| Windsor | 43,840 | May 3 | Oct 6 | 154 days | 5b |
| Erie | 40,904 | May 7 | Oct 5 | 151 days | 5b |
| Northglenn | 38,893 | May 2 | Oct 11 | 160 days | 6a |
| Englewood | 35,305 | May 2 | Oct 11 | 160 days | 6a |
| Wheat Ridge | 32,081 | May 5 | Oct 5 | 151 days | 6a |
| Lafayette | 30,116 | May 2 | Oct 11 | 160 days | 6a |
| Fountain | 29,450 | May 3 | Oct 8 | 158 days | 6a |
| Evans | 22,500 | May 2 | Oct 8 | 159 days | 5b |
| Johnstown | 22,433 | May 10 | Oct 1 | 142 days | 5b |
| Montrose | 21,583 | Apr 28 | Oct 14 | 167 days | 6b |
| Louisville | 20,581 | May 6 | Oct 5 | 151 days | 6a |
| Golden | 20,390 | May 3 | Oct 7 | 155 days | 5b |
| Firestone | 20,129 | May 7 | Oct 5 | 151 days | 5b |
| Durango | 19,733 | May 21 | Oct 2 | 134 days | 6b |
| Frederick | 18,241 | May 7 | Oct 5 | 151 days | 5b |
| Cañon City | 17,030 | May 4 | Oct 7 | 153 days | 6a |
| Castle Pines | 15,583 | May 9 | Oct 2 | 143 days | 5b |
| Greenwood Village | 15,323 | May 7 | Oct 8 | 152 days | 6a |
| Lone Tree | 15,278 | May 5 | Oct 8 | 154 days | 6a |
| Berthoud | 14,080 | May 7 | Oct 5 | 151 days | 5b |
| Federal Heights | 14,075 | May 2 | Oct 11 | 160 days | 6a |
| Fruita | 14,003 | Apr 27 | Oct 11 | 164 days | 7a |
| Monument | 13,813 | May 17 | Oct 1 | 136 days | 5b |
| Superior | 13,637 | May 6 | Oct 5 | 151 days | 6a |
| Steamboat Springs | 13,557 | Jun 9 | Sep 12 | 93 days | 5b |
| Sterling | 13,054 | Apr 30 | Oct 9 | 161 days | 5b |
| Wellington | 12,169 | May 3 | Oct 6 | 154 days | 5b |
| Fort Morgan | 11,841 | May 6 | Oct 6 | 153 days | 5b |
| Severance | 11,841 | May 3 | Oct 6 | 154 days | 5b |
| Timnath | 11,600 | May 3 | Oct 6 | 154 days | 5b |
| Rifle | 10,844 | May 11 | Oct 4 | 143 days | 6a |
| Fort Lupton | 10,402 | May 3 | Oct 7 | 155 days | 5b |
| Glenwood Springs | 10,395 | May 13 | Oct 3 | 142 days | 6a |
| Alamosa | 9,849 | May 30 | Sep 17 | 108 days | 4b |
| Delta | 9,802 | May 1 | Oct 7 | 159 days | 6b |
| Gypsum | 9,212 | May 1 | Oct 14 | 164 days | 5b |
| Milliken | 9,183 | May 2 | Oct 8 | 159 days | 5b |
| Cortez | 9,126 | May 12 | Oct 7 | 147 days | 7a |
| Craig | 8,874 | Jun 6 | Sep 12 | 96 days | 5b |
| Lochbuie | 8,776 | May 3 | Oct 7 | 155 days | 5b |
| Trinidad | 8,091 | Apr 30 | Oct 15 | 167 days | 6a |
| Woodland Park | 8,014 | Jun 1 | Sep 21 | 110 days | 5b |
| Lamar | 7,588 | Apr 30 | Oct 10 | 163 days | 6a |
| Eagle | 7,280 | May 1 | Oct 14 | 164 days | 5b |
| Mead | 7,042 | May 7 | Oct 5 | 151 days | 5b |
| La Junta | 6,864 | Apr 26 | Oct 15 | 171 days | 6a |
| Dacono | 6,844 | May 7 | Oct 5 | 151 days | 5b |
| Gunnison | 6,836 | Jun 21 | Sep 5 | 74 days | 5b |
| Carbondale | 6,762 | May 13 | Oct 3 | 142 days | 6a |
| Aspen | 6,489 | Jun 2 | Sep 23 | 113 days | 5b |
| Cherry Hills Village | 6,389 | May 7 | Oct 8 | 152 days | 6a |
| Avon | 6,184 | Jun 21 | Sep 7 | 77 days | 6a |
| Salida | 5,985 | May 29 | Sep 20 | 112 days | 6a |
| Sheridan | 5,972 | May 2 | Oct 11 | 160 days | 6a |
| Eaton | 5,848 | May 2 | Oct 8 | 159 days | 5a |
| Estes Park | 5,780 | May 30 | Sep 17 | 109 days | 5a |
| Silverthorne | 5,418 | Jun 21 | Sep 7 | 77 days | 5a |
| Brush | 5,337 | May 6 | Oct 6 | 153 days | 5b |
| Breckenridge | 5,015 | Jun 21 | Sep 7 | 77 days | 5a |