Massachusetts frost dates: O
| City | Last frost | First frost | Season | Zone |
|---|---|---|---|---|
| Oak Bluffs | May 7 | Oct 9 | 155 d | 7a |
| Oakham | May 12 | Oct 1 | 142 d | 6a |
| Ocean Bluff | Apr 15 | Nov 1 | 200 d | 7a |
| Onset | Apr 21 | Oct 24 | 186 d | 7a |
| Orange | May 4 | Oct 8 | 157 d | 5b |
| Orleans | Apr 13 | Nov 4 | 205 d | 7b |
| Osterville | Apr 16 | Oct 30 | 197 d | 7a |
| Otis | May 7 | Oct 3 | 149 d | 5b |
| Oxford | May 1 | Oct 10 | 162 d | 6b |