South Dakota frost dates: R
| City | Last frost | First frost | Season | Zone |
|---|---|---|---|---|
| Ralph | May 18 | Sep 23 | 128 d | 4b |
| Ramona | May 5 | Sep 30 | 148 d | 4b |
| Rapid City | May 3 | Oct 8 | 158 d | 5a |
| Raymond | May 5 | Oct 5 | 153 d | 4b |
| Redfield | May 8 | Oct 1 | 146 d | 4b |
| Redig | May 15 | Sep 24 | 132 d | 4b |
| Ree Heights | May 12 | Oct 1 | 142 d | 4b |
| Reliance | May 12 | Sep 28 | 139 d | 5a |
| Renner | May 1 | Oct 6 | 158 d | 5a |
| Reva | May 20 | Sep 19 | 122 d | 4b |
| Revillo | May 5 | Oct 2 | 150 d | 4b |
| Ridgeview | May 5 | Oct 4 | 152 d | 4b |
| Rockham | May 8 | Oct 1 | 146 d | 4b |
| Roscoe | May 7 | Oct 3 | 149 d | 4b |
| Rosebud | May 9 | Oct 1 | 145 d | 5a |
| Rosholt | May 4 | Oct 3 | 152 d | 4b |
| Roslyn | May 1 | Oct 12 | 164 d | 4b |
| Rutland | May 2 | Oct 5 | 156 d | 4b |