Washington frost dates: B
| City | Last frost | First frost | Season | Zone |
|---|---|---|---|---|
| Bainbridge Island | Mar 29 | Nov 14 | 230 d | 9a |
| Baring | Apr 14 | Oct 29 | 198 d | 8a |
| Battle Ground | Apr 26 | Oct 16 | 173 d | 8b |
| Bay Center | Apr 26 | Oct 17 | 174 d | 9a |
| Beaver | Apr 26 | Oct 25 | 182 d | 8b |
| Belfair | Mar 24 | Nov 15 | 236 d | 8b |
| Bellevue | Mar 8 | Nov 23 | 260 d | 9a |
| Bellingham | Apr 1 | Nov 2 | 215 d | 8b |
| Belmont | May 7 | Sep 28 | 144 d | 6b |
| Benge | May 13 | Sep 26 | 136 d | 7a |
| Benton City | Apr 6 | Oct 24 | 201 d | 7b |
| Beverly | Apr 23 | Oct 12 | 172 d | 7b |
| Bickleton | May 16 | Oct 9 | 146 d | 7b |
| Bingen | Apr 20 | Oct 13 | 176 d | 7b |
| Black Diamond | Apr 20 | Oct 25 | 188 d | 8b |
| Blaine | Mar 31 | Nov 4 | 218 d | 8b |
| Blakely Island | Feb 26 | Nov 29 | 276 d | 9a |
| Bonney Lake | Apr 11 | Oct 30 | 202 d | 8b |
| Bothell | Mar 8 | Nov 23 | 260 d | 8b |
| Bow | Mar 24 | Nov 3 | 224 d | 8b |
| Boyds | May 8 | Oct 1 | 146 d | 6b |
| Bremerton | Mar 29 | Nov 14 | 230 d | 9a |
| Brewster | Apr 26 | Oct 11 | 168 d | 7a |
| Bridgeport | Apr 26 | Oct 11 | 168 d | 7a |
| Brinnon | Apr 11 | Oct 28 | 200 d | 8b |
| Brownstown | Apr 21 | Oct 15 | 177 d | 7a |
| Brush Prairie | Apr 26 | Oct 16 | 173 d | 8b |
| Buckley | Apr 7 | Oct 30 | 206 d | 8b |
| Bucoda | Apr 22 | Oct 27 | 188 d | 8b |
| Buena | Apr 21 | Oct 15 | 177 d | 7a |
| Burbank | Apr 7 | Oct 22 | 198 d | 7a |
| Burley | Mar 29 | Nov 14 | 230 d | 9a |
| Burlington | Mar 24 | Nov 3 | 224 d | 8b |
| Burton | Mar 2 | Nov 23 | 266 d | 9a |