Montana frost dates: L
| City | Last frost | First frost | Season | Zone |
|---|---|---|---|---|
| Lake Mc Donald | May 9 | Oct 1 | 145 d | 5a |
| Lakeside | May 12 | Sep 25 | 136 d | 6a |
| Lambert | May 11 | Sep 27 | 139 d | 4a |
| Lame Deer | May 23 | Sep 15 | 115 d | 5a |
| Larslan | Jun 5 | Sep 2 | 89 d | 3b |
| Laurel | May 5 | Oct 3 | 151 d | 5a |
| Lavina | May 22 | Sep 15 | 116 d | 4b |
| Ledger | May 16 | Sep 23 | 130 d | 4a |
| Lewistown | May 14 | Sep 28 | 137 d | 4b |
| Libby | May 10 | Sep 26 | 139 d | 6a |
| Lima | Jun 11 | Sep 10 | 91 d | 5a |
| Lincoln | frost any month | 4b | ||
| Lindsay | May 26 | Sep 17 | 114 d | 4b |
| Livingston | May 27 | Sep 14 | 110 d | 5a |
| Lloyd | May 23 | Sep 23 | 123 d | 4b |
| Lodge Grass | May 21 | Sep 17 | 119 d | 5a |
| Lolo | May 16 | Sep 26 | 133 d | 5b |
| Loma | May 20 | Sep 19 | 122 d | 4a |
| Lonepine | May 15 | Sep 28 | 136 d | 6a |
| Loring | May 19 | Sep 22 | 126 d | 3b |
| Lothair | May 24 | Sep 17 | 116 d | 4a |