Washington frost dates: F
| City | Last frost | First frost | Season | Zone |
|---|---|---|---|---|
| Fairchild Air Force Base | May 10 | Sep 26 | 139 d | 6b |
| Fairfield | May 11 | Oct 5 | 147 d | 6b |
| Fall City | Mar 30 | Nov 7 | 222 d | 8b |
| Farmington | May 15 | Sep 21 | 129 d | 6b |
| Federal Way | Mar 20 | Nov 10 | 235 d | 8b |
| Ferndale | Mar 31 | Oct 30 | 213 d | 8b |
| Ford | May 22 | Sep 14 | 115 d | 6b |
| Forks | Apr 26 | Oct 25 | 182 d | 8b |
| Four Lakes | Apr 26 | Oct 12 | 169 d | 6b |
| Fox Island | Mar 11 | Nov 21 | 255 d | 9a |
| Freeland | Mar 1 | Nov 28 | 272 d | 8b |
| Friday Harbor | Mar 26 | Nov 10 | 229 d | 9a |
| Fruitland | Jun 6 | Sep 11 | 97 d | 7a |