Montana frost dates
Across 216 weather stations in Montana, the median last spring frost runs from Apr 30 in Norris Madison Power House to Jun 18 in Tizer Gardens, and the first fall frost from Sep 2 to Oct 15.
Montana at a glance
- Weather stations
- 216
- Earliest last frost
- Apr 30 Norris Madison Power House
- Latest last frost
- Jun 18 Tizer Gardens
- Longest season
- 165 days Bigfork
- Typical season
- about 123 frost-free days
- Hardiness zones
- Zones 3b to 6b
Frost dates by weather station
| Weather station | Last spring frost | First fall frost | Frost-free days | Zone |
|---|---|---|---|---|
| Adel | Jun 4 | Sep 12 | 98 | 4b |
| Alberton | May 18 | Sep 25 | 126 | 5b |
| Albion | Jun 2 | Sep 6 | 95 | 4b |
| Alder | Jun 6 | Sep 14 | 98 | 5a |
| Anaconda | Jun 1 | Sep 14 | 105 | 4b |
| Augusta | May 19 | Sep 21 | 125 | 4b |
| Austin | Jun 4 | Sep 14 | 100 | 4b |
| Baker | May 12 | Sep 26 | 135 | 4b |
| Baker Municipal Airport | May 16 | Sep 26 | 132 | 4b |
| Biddle | May 14 | Sep 28 | 134 | 4b |
| Big Sandy | May 17 | Sep 25 | 128 | 4a |
| Big Timber | May 14 | Sep 26 | 133 | 5a |
| Bigfork | May 1 | Oct 15 | 165 | 5b |
| Billings | May 5 | Oct 3 | 149 | 5a |
| Billings Logan International Airport | May 4 | Oct 7 | 156 | 5a |
| Billings Water Plant | May 10 | Oct 1 | 142 | 5a |
| Blackleaf | Jun 9 | Sep 3 | 86 | 4b |
| Boulder | Jun 7 | Sep 8 | 90 | 5a |
| Bozeman Experiment Farm | May 23 | Sep 23 | 123 | 5a |
| Bozeman Gallatin Field | May 26 | Sep 16 | 112 | 5a |
| Bozeman Montana State University | May 26 | Sep 22 | 116 | 5a |
| Brady (the Knees) | May 13 | Sep 29 | 137 | 4a |
| Brandenberg | May 18 | Sep 22 | 126 | 4b |
| Bredette | May 20 | Sep 21 | 122 | 4a |
| Bridger | May 14 | Sep 24 | 129 | 5a |
| Broadus | May 16 | Sep 28 | 135 | 4b |
| Brockway | May 20 | Sep 19 | 121 | 4a |
| Busby | May 23 | Sep 15 | 113 | 5a |
| Butte Bert Mooney Airport | Jun 13 | Sep 5 | 83 | 5a |
| Bynum | May 16 | Sep 27 | 133 | 4b |
| Carlyle | May 18 | Sep 29 | 134 | 4a |
| Carter | May 23 | Sep 23 | 120 | 4b |
| Cascade | May 21 | Sep 19 | 120 | 4b |
| Chester | May 24 | Sep 17 | 115 | 4a |
| Chinook | May 14 | Sep 23 | 130 | 3b |
| Chinook 35 mi SE | May 23 | Sep 23 | 121 | 4b |
| Choteau | May 28 | Sep 12 | 104 | 4b |
| Choteau 8 mi NE | May 20 | Sep 22 | 123 | 4a |
| Circle | May 17 | Sep 22 | 126 | 4a |
| Cohagen | May 25 | Sep 14 | 110 | 4a |
| Colstrip | May 15 | Sep 30 | 138 | 5a |
| Columbus | May 27 | Sep 14 | 108 | 5a |
| Conrad | May 20 | Sep 19 | 119 | 4a |
| Content | May 25 | Sep 14 | 110 | 4a |
| Creston | May 12 | Sep 25 | 134 | 6a |
| Culbertson | May 21 | Sep 20 | 120 | 4a |
| Cut Bank Municipal Airport | May 24 | Sep 15 | 113 | 4a |
| Darby | May 24 | Sep 23 | 118 | 5b |
| Del Bonita | May 28 | Sep 16 | 110 | 4a |
| Denton | Jun 1 | Sep 11 | 101 | 4b |
| Dillon Airport | Jun 2 | Sep 13 | 101 | 4b |
| Dillon U of Montana Western | Jun 5 | Sep 13 | 98 | 5a |
| Divide | Jun 10 | Sep 7 | 85 | 5a |
| Dunkirk | May 23 | Sep 14 | 112 | 4a |
| East Glacier | Jun 8 | Sep 5 | 88 | 4a |
| Ekalaka | May 20 | Sep 23 | 126 | 4b |
| Elliston | Jun 9 | Sep 8 | 91 | 4b |
| Ennis | Jun 16 | Sep 4 | 78 | 5a |
| Eureka Ranger Station | May 11 | Sep 27 | 138 | 5b |
| Fairfield | May 13 | Sep 27 | 135 | 4b |
| Flatwillow | May 16 | Sep 28 | 132 | 4b |
| Forsyth | May 9 | Sep 29 | 142 | 4b |
| Fort Assiniboine | May 15 | Sep 24 | 130 | 3b |
| Fort Belknap | May 16 | Sep 22 | 128 | 4a |
| Fort Benton | May 15 | Sep 22 | 129 | 4a |
| Fort Peck Power Plant | May 8 | Oct 1 | 145 | 4a |
| Fortine | May 16 | Sep 18 | 121 | 5a |
| Gardiner | May 21 | Sep 27 | 128 | 4b |
| Geraldine | May 14 | Sep 26 | 134 | 4b |
| Gibson | May 27 | Sep 18 | 113 | 4b |
| Gibson Dam | Jun 12 | Sep 8 | 88 | 4b |
| Gildford | May 24 | Sep 15 | 114 | 3b |
| Glasgow | May 3 | Oct 1 | 151 | 4a |
| Glasgow International Airport | May 6 | Sep 30 | 145 | 4a |
| Glendive | May 3 | Oct 4 | 153 | 4a |
| Grass Range | May 20 | Sep 24 | 126 | 4b |
| Great Falls | May 12 | Sep 28 | 138 | 4b |
| Great Falls 16st | May 6 | Oct 1 | 147 | 4b |
| Great Falls International Airport | May 19 | Sep 24 | 126 | 4b |
| Hamilton | May 21 | Sep 22 | 122 | 5b |
| Hardin | May 13 | Sep 29 | 135 | 4b |
| Harlem | May 16 | Sep 21 | 125 | 4a |
| Harlem 20 mi S | May 24 | Sep 22 | 118 | 4a |
| Harlowton | May 23 | Sep 16 | 113 | 4b |
| Harlowton 11 mi NW | May 30 | Sep 20 | 110 | 4b |
| Havre City County Airport | May 15 | Sep 23 | 129 | 3b |
| Hebgen Dam | Jun 15 | Sep 10 | 87 | 4b |
| Helena Regional Airport | May 9 | Sep 30 | 142 | 5a |
| Heron | May 20 | Sep 20 | 119 | 6b |
| Highwood | May 7 | Oct 2 | 149 | 4b |
| Hinsdale | May 15 | Sep 26 | 132 | 3b |
| Holter Dam | May 19 | Sep 24 | 124 | 4b |
| Hungry Horse Dam | May 9 | Oct 1 | 141 | 5b |
| Huntley Experiment Station | May 12 | Sep 25 | 136 | 4b |
| Hysham | May 10 | Sep 29 | 141 | 4b |
| Hysham 25 mi SSE | May 26 | Sep 16 | 111 | 4b |
| Ingomar | May 21 | Sep 19 | 120 | 4b |
| Joliet | May 29 | Sep 15 | 107 | 5a |
| Joplin | May 21 | Sep 19 | 119 | 4a |
| Jordan | May 21 | Sep 18 | 118 | 4a |
| Jordan Airport | May 18 | Sep 20 | 123 | 4a |
| Judith Gap | Jun 1 | Sep 15 | 104 | 4b |
| Judith Gap 13 mi E | Jun 3 | Sep 15 | 100 | 4b |
| Kalispell Glacier Airport | May 31 | Sep 10 | 100 | 5b |
| Laurin | May 24 | Sep 22 | 117 | 5a |
| Lewistown | May 14 | Sep 28 | 135 | 4b |
| Lewistown 11 mi ESE | May 19 | Sep 25 | 128 | 4b |
| Lewistown 11 mi SSE | May 31 | Sep 14 | 105 | 4b |
| Lewistown 42 mi WSW | Jun 15 | Sep 4 | 77 | 4b |
| Lewistown Municipal Airport | May 23 | Sep 21 | 119 | 4b |
| Libby | May 10 | Sep 26 | 137 | 6a |
| Libby Dam (base) | May 11 | Oct 1 | 142 | 6a |
| Libby Ranger Station | May 23 | Sep 21 | 120 | 6a |
| Lima | Jun 11 | Sep 10 | 89 | 5a |
| Lindbergh Lake | May 20 | Sep 22 | 120 | 5a |
| Livingston | May 19 | Sep 25 | 125 | 5a |
| Livingston Mission Field | May 27 | Sep 14 | 108 | 5a |
| Logan Landfill | May 26 | Sep 15 | 111 | 5a |
| Loma | May 20 | Sep 19 | 120 | 4a |
| Malta | May 10 | Sep 29 | 139 | 4a |
| Malta 35 mi S | May 16 | Sep 23 | 128 | 4a |
| Malta 7 mi E | May 7 | Sep 28 | 143 | 3b |
| Martinsdale | Jun 3 | Sep 8 | 94 | 4b |
| Medicine Lake | May 16 | Sep 18 | 125 | 3b |
| Melstone | May 10 | Sep 29 | 141 | 4b |
| Melville | Jun 9 | Sep 7 | 88 | 4b |
| Mildred | May 20 | Sep 22 | 124 | 4a |
| Miles City F Wiley Field | May 8 | Sep 30 | 144 | 4b |
| Millegan | Jun 11 | Sep 6 | 86 | 4b |
| Missoula 2 mi NE | May 10 | Oct 1 | 143 | 5b |
| Missoula 6 mi NW | May 6 | Oct 4 | 151 | 5b |
| Missoula International Airport | May 16 | Sep 26 | 130 | 5b |
| Mizpah | May 22 | Sep 15 | 117 | 4a |
| Moccasin Experiment Station | May 28 | Sep 20 | 112 | 4b |
| Moorhead | May 17 | Sep 22 | 126 | 4b |
| Mosby | May 5 | Oct 4 | 151 | 4b |
| Mystic Lake | Jun 5 | Sep 14 | 99 | 5a |
| Nashua | May 12 | Sep 24 | 134 | 4a |
| Neihart | Jun 6 | Sep 12 | 99 | 4b |
| Norris Madison Power House | Apr 30 | Oct 10 | 162 | 5a |
| Nye | Jun 1 | Sep 11 | 100 | 5a |
| Opheim 10 mi N | Jun 1 | Sep 7 | 99 | 3b |
| Opheim 12 mi SSE | Jun 5 | Sep 2 | 89 | 3b |
| Plentywood | May 25 | Sep 14 | 111 | 3b |
| Plevna | May 21 | Sep 20 | 121 | 4a |
| Polson | May 10 | Oct 5 | 147 | 6a |
| Pompeys Pillar | May 22 | Sep 22 | 121 | 4b |
| Port of Morgan | May 19 | Sep 22 | 124 | 3b |
| Powderville | May 13 | Sep 25 | 132 | 4b |
| Rapelje | May 24 | Sep 21 | 116 | 4b |
| Raymond Border Station | May 19 | Sep 23 | 125 | 4a |
| Raynesford | May 22 | Sep 23 | 123 | 4b |
| Red Lodge | Jun 3 | Sep 19 | 106 | 5a |
| Redstone | May 28 | Sep 7 | 101 | 3b |
| Ridgeway | May 17 | Sep 22 | 127 | 4b |
| Rock Springs | May 15 | Sep 25 | 132 | 4a |
| Rogers Pass | May 21 | Sep 15 | 115 | 4b |
| Roundup | May 20 | Sep 21 | 124 | 4b |
| Roundup 15 mi SW | May 22 | Sep 15 | 114 | 4b |
| Roy | May 14 | Sep 24 | 134 | 4b |
| Rudyard 19 mi S | May 23 | Sep 19 | 119 | 4a |
| Rudyard 21 mi N | May 30 | Sep 11 | 103 | 4a |
| Ryegate | May 17 | Sep 23 | 127 | 4b |
| Ryegate 18 mi NNW | May 26 | Sep 18 | 112 | 4b |
| Saco | May 15 | Sep 23 | 130 | 3b |
| Saint Ignatius | May 12 | Oct 2 | 142 | 6a |
| Sand Creek | May 12 | Sep 27 | 136 | 4b |
| Savage | May 12 | Sep 25 | 135 | 4a |
| Scobey | May 28 | Sep 6 | 99 | 3b |
| Shelby | May 23 | Sep 16 | 115 | 4a |
| Shonkin | May 24 | Sep 21 | 119 | 4b |
| Sidney | May 11 | Sep 27 | 137 | 4a |
| Simpson - Wildhorse | May 26 | Sep 15 | 110 | 3b |
| Skq Dam | May 15 | Sep 28 | 134 | 6a |
| Sonnette | May 25 | Sep 19 | 115 | 4b |
| St. Marie | May 13 | Sep 27 | 134 | 4a |
| St. Mary | Jun 12 | Sep 5 | 82 | 4b |
| St. Mary 1 mi SSW | Jun 3 | Sep 8 | 94 | 4b |
| Stanford | May 25 | Sep 21 | 118 | 4b |
| Stevensville | May 22 | Sep 19 | 115 | 5b |
| Sun River | Jun 2 | Sep 10 | 96 | 4a |
| Sunburst | May 17 | Sep 25 | 129 | 4a |
| Superior | May 17 | Sep 23 | 125 | 6a |
| Swan Lake | May 17 | Sep 19 | 121 | 5b |
| Sweetgrass | May 15 | Sep 25 | 132 | 4a |
| Terry | May 12 | Sep 28 | 137 | 4a |
| Terry 21 mi NNW | May 26 | Sep 17 | 113 | 4b |
| Thompson Falls Powerhouse | May 7 | Oct 4 | 150 | 6a |
| Tiber Dam | May 16 | Sep 23 | 129 | 4a |
| Tizer Gardens | Jun 18 | Sep 5 | 81 | 4b |
| Townsend | May 19 | Sep 19 | 122 | 4b |
| Trident | May 9 | Sep 27 | 139 | 5a |
| Trout Creek Ranger Station | May 20 | Sep 21 | 122 | 6a |
| Troy | May 14 | Sep 25 | 132 | 6a |
| Turner | May 19 | Sep 21 | 124 | 4a |
| Twin Bridges | Jun 8 | Sep 2 | 82 | 5a |
| Valentine | May 18 | Sep 21 | 124 | 4b |
| Valier | May 17 | Sep 24 | 129 | 4b |
| Vida | May 16 | Sep 22 | 129 | 4a |
| Virginia City | Jun 4 | Sep 18 | 106 | 5a |
| West Glacier | May 18 | Sep 20 | 124 | 5a |
| Westby | May 18 | Sep 21 | 125 | 3b |
| Western Ag Research Center | May 23 | Sep 21 | 118 | 5b |
| White Sulphur Springs | Jun 4 | Sep 11 | 97 | 4b |
| Whitefish | May 16 | Sep 25 | 129 | 5a |
| Wibaux | May 27 | Sep 16 | 112 | 4a |
| Wilsall 1 mi S | Jun 4 | Sep 6 | 92 | 4b |
| Wilsall 8 mi ENE | Jun 8 | Sep 7 | 89 | 4b |
| Winifred | May 16 | Sep 23 | 127 | 4b |
| Wolf Point | May 8 | Sep 28 | 143 | 4a |
| Wolf Point 29 mi ENE | May 24 | Sep 14 | 110 | 4a |
| Wolf Point 34 mi NE | May 13 | Sep 28 | 137 | 4a |
| Wolf Point International Airport | May 16 | Sep 20 | 125 | 4a |
| Wyola | May 21 | Sep 17 | 117 | 4b |
| Yellowtail Dam | May 7 | Oct 5 | 151 | 5a |
| Zortman | May 18 | Sep 23 | 126 | 4b |
Median dates from NOAA 1991–2020 climate normals. How to read them.