Colorado frost dates: N
| City | Last frost | First frost | Season | Zone |
|---|---|---|---|---|
| Nathrop | May 27 | Sep 23 | 119 d | 5b |
| Naturita | Apr 26 | Oct 18 | 175 d | 6b |
| Nederland | Jun 21 | Sep 2 | 73 d | 5b |
| New Castle | May 23 | Sep 25 | 125 d | 6a |
| New Raymer | May 9 | Oct 4 | 148 d | 5a |
| Niwot | May 7 | Oct 5 | 151 d | 6a |
| Norwood | May 21 | Oct 1 | 133 d | 6a |
| Nucla | Apr 26 | Oct 18 | 175 d | 6a |
| Nunn | May 13 | Sep 27 | 137 d | 5a |