Pennsylvania frost dates: U
| City | Last frost | First frost | Season | Zone |
|---|---|---|---|---|
| Uledi | Apr 30 | Oct 18 | 171 d | 6b |
| Ulster | May 2 | Oct 15 | 166 d | 6a |
| Ulysses | May 14 | Oct 4 | 143 d | 5b |
| Union City | May 7 | Oct 10 | 156 d | 6a |
| Union Dale | May 14 | Oct 1 | 140 d | 5b |
| Uniontown | Apr 30 | Oct 18 | 171 d | 6b |
| Unionville | Apr 19 | Oct 26 | 190 d | 7a |
| United | May 1 | Oct 13 | 165 d | 6b |
| Unityville | May 4 | Oct 11 | 160 d | 6a |
| University Park | Apr 20 | Oct 26 | 189 d | 6b |
| Upper Black Eddy | Apr 29 | Oct 16 | 170 d | 6b |
| Upper Darby | Mar 30 | Nov 17 | 232 d | 7b |
| Upperstrasburg | Apr 18 | Oct 25 | 190 d | 7a |
| Ursina | Apr 30 | Oct 18 | 171 d | 6a |
| Utica | May 2 | Oct 23 | 174 d | 6a |
| Uwchland | Apr 11 | Nov 1 | 204 d | 7a |