Wisconsin frost dates: J
| City | Last frost | First frost | Season | Zone |
|---|---|---|---|---|
| Jackson | Apr 30 | Oct 15 | 168 d | 5b |
| Janesville | Apr 26 | Oct 15 | 172 d | 5b |
| Jefferson | Apr 25 | Oct 18 | 176 d | 5b |
| Jim Falls | May 1 | Oct 8 | 160 d | 4b |
| Johnson Creek | Apr 25 | Oct 18 | 176 d | 5b |
| Juda | Apr 29 | Oct 12 | 166 d | 5a |
| Jump River | May 20 | Sep 23 | 126 d | 4a |
| Junction City | May 4 | Oct 7 | 156 d | 4b |
| Juneau | May 1 | Oct 10 | 162 d | 5a |