Minnesota frost dates: O
| City | Last frost | First frost | Season | Zone |
|---|---|---|---|---|
| Oak Island | May 16 | Sep 24 | 131 d | |
| Oak Park | May 8 | Oct 1 | 146 d | 4b |
| Odessa | May 1 | Oct 8 | 160 d | 4b |
| Odin | Apr 30 | Oct 7 | 160 d | 5a |
| Ogema | May 7 | Sep 28 | 144 d | 4a |
| Ogilvie | May 9 | Sep 30 | 144 d | 4a |
| Okabena | May 2 | Oct 2 | 153 d | 5a |
| Oklee | May 15 | Sep 26 | 134 d | 3b |
| Olivia | May 6 | Oct 1 | 148 d | 4b |
| Onamia | May 10 | Oct 3 | 146 d | 4a |
| Ormsby | Apr 30 | Oct 7 | 160 d | 5a |
| Oronoco | May 12 | Sep 28 | 139 d | 4b |
| Orr | Jun 2 | Sep 15 | 105 d | 3b |
| Ortonville | May 2 | Oct 4 | 155 d | 4b |
| Osage | May 14 | Sep 25 | 134 d | 3b |
| Osakis | May 2 | Oct 8 | 159 d | 4b |
| Oslo | May 5 | Oct 2 | 150 d | 4a |
| Osseo | Apr 30 | Oct 8 | 161 d | 5a |
| Ostrander | May 6 | Oct 1 | 148 d | 4b |
| Ottertail | May 5 | Oct 5 | 153 d | 4a |
| Outing | May 6 | Oct 7 | 154 d | 4a |
| Owatonna | May 5 | Oct 6 | 154 d | 4b |