Colorado frost dates: R
| City | Last frost | First frost | Season | Zone |
|---|---|---|---|---|
| Ramah | May 9 | Oct 4 | 148 d | 5b |
| Rand | frost any month | 4b | ||
| Rangely | May 15 | Oct 1 | 139 d | 6a |
| Red Cliff | Jun 21 | Sep 7 | 78 d | 5a |
| Red Feather Lakes | Jun 5 | Sep 16 | 103 d | 5a |
| Redvale | May 25 | Oct 1 | 129 d | 6b |
| Rico | frost any month | 5b | ||
| Ridgway | Jun 11 | Sep 13 | 94 d | 6a |
| Rifle | May 23 | Sep 25 | 125 d | 6a |
| Rockvale | May 4 | Oct 7 | 156 d | 6a |
| Rocky Ford | May 1 | Oct 8 | 160 d | 6a |
| Roggen | May 6 | Oct 6 | 153 d | 5b |
| Rollinsville | Jun 5 | Sep 16 | 103 d | 5b |
| Romeo | May 28 | Sep 21 | 116 d | 5a |
| Rush | May 9 | Oct 4 | 148 d | 5b |
| Rye | May 5 | Oct 10 | 158 d | 6a |