Washington frost dates: C
| City | Last frost | First frost | Season | Zone |
|---|---|---|---|---|
| Camano Island | Mar 17 | Nov 11 | 239 d | 8b |
| Camas | Mar 16 | Nov 20 | 249 d | 8b |
| Camp Murray | Apr 11 | Oct 30 | 202 d | 8b |
| Carbonado | Apr 7 | Oct 30 | 206 d | 8b |
| Carlsborg | Apr 21 | Oct 20 | 182 d | 8b |
| Carlton | Apr 21 | Oct 15 | 177 d | 6b |
| Carnation | Mar 30 | Nov 7 | 222 d | 8b |
| Carrolls | Apr 8 | Nov 5 | 211 d | 8b |
| Carson | Mar 24 | Nov 20 | 241 d | 8a |
| Cashmere | May 10 | Sep 30 | 143 d | 7a |
| Castle Rock | Apr 8 | Nov 5 | 211 d | 8b |
| Cathlamet | Apr 24 | Oct 24 | 183 d | 8b |
| Centerville | May 19 | Sep 25 | 129 d | 7b |
| Centralia | Apr 22 | Oct 27 | 188 d | 8b |
| Chattaroy | May 22 | Sep 14 | 115 d | 6b |
| Chehalis | Apr 22 | Oct 27 | 188 d | 8a |
| Chelan | Apr 17 | Oct 22 | 188 d | 7a |
| Chelan Falls | Apr 17 | Oct 22 | 188 d | 7b |
| Cheney | May 30 | Sep 4 | 97 d | 6b |
| Chewelah | May 16 | Sep 15 | 122 d | 6a |
| Chimacum | Mar 1 | Nov 28 | 272 d | 8b |
| Chinook | Apr 6 | Oct 26 | 203 d | 8b |
| Cinebar | Apr 7 | Nov 13 | 220 d | 8b |
| Clallam Bay | Apr 26 | Oct 25 | 182 d | 9a |
| Clarkston | Apr 6 | Oct 26 | 203 d | 7b |
| Clayton | May 22 | Sep 14 | 115 d | 6a |
| Cle Elum | May 13 | Sep 25 | 135 d | 7a |
| Clearlake | Mar 27 | Nov 6 | 224 d | 8b |
| Clinton | Mar 9 | Nov 17 | 253 d | 8b |
| Colbert | May 22 | Sep 14 | 115 d | 6b |
| Colfax | May 6 | Sep 29 | 146 d | 7a |
| College Place | May 2 | Oct 1 | 152 d | 7a |
| Colton | Apr 29 | Oct 2 | 156 d | 7a |
| Colville | May 2 | Oct 2 | 153 d | 6a |
| Conconully | Apr 30 | Oct 7 | 160 d | 6b |
| Concrete | Mar 28 | Nov 14 | 231 d | 8a |
| Connell | Apr 30 | Oct 12 | 165 d | 7a |
| Conway | Mar 24 | Nov 3 | 224 d | 8b |
| Copalis Beach | Apr 26 | Oct 22 | 179 d | 9a |
| Copalis Crossing | Apr 26 | Oct 22 | 179 d | 9a |
| Cosmopolis | Mar 29 | Nov 15 | 231 d | 8b |
| Cougar | Apr 1 | Nov 18 | 231 d | 8a |
| Coulee City | May 2 | Oct 12 | 163 d | 6b |
| Coulee Dam | Apr 22 | Oct 21 | 182 d | 7a |
| Coupeville | Mar 17 | Nov 11 | 239 d | 8b |
| Cowiche | Apr 8 | Oct 23 | 198 d | 7a |
| Creston | Jun 1 | Sep 22 | 113 d | 6b |
| Curlew | May 30 | Sep 10 | 103 d | 6a |
| Curtis | Apr 5 | Oct 25 | 203 d | 8a |
| Cusick | May 12 | Sep 21 | 132 d | 6a |
| Custer | Mar 31 | Nov 4 | 218 d | 8b |