North Dakota frost dates: R
| City | Last frost | First frost | Season | Zone |
|---|---|---|---|---|
| Raleigh | May 13 | Sep 27 | 137 d | 4a |
| Ray | May 11 | Sep 26 | 138 d | 4a |
| Reeder | May 24 | Sep 18 | 117 d | 4b |
| Regan | May 11 | Sep 30 | 142 d | 4a |
| Regent | May 16 | Sep 25 | 132 d | 4a |
| Reynolds | May 10 | Oct 1 | 144 d | 4a |
| Rhame | May 16 | Sep 25 | 132 d | 4b |
| Richardton | May 9 | Oct 1 | 145 d | 4a |
| Riverdale | May 12 | Oct 3 | 144 d | 4a |
| Robinson | May 13 | Sep 29 | 139 d | 4a |
| Rocklake | May 18 | Sep 23 | 128 d | 3b |
| Rogers | May 13 | Sep 26 | 136 d | 4a |
| Rolette | May 22 | Sep 20 | 121 d | 3b |
| Rolla | May 20 | Sep 26 | 129 d | 3b |
| Roseglen | May 14 | Sep 26 | 135 d | 4a |
| Ross | May 17 | Sep 23 | 129 d | 4a |
| Rugby | May 17 | Sep 23 | 129 d | 3b |
| Ruso | May 16 | Sep 28 | 135 d | 4a |
| Rutland | May 7 | Oct 1 | 147 d | 4a |
| Ryder | May 10 | Sep 28 | 141 d | 4a |