Last frost dates in Montana
216 NOAA weather stations in Montana have thirty years of frost records. The median station sees its last 32 °F night around May 20; across the state that ranges from Apr 30 to Jun 18, so pick the station nearest you rather than a state-wide figure.
| NORRIS MADISON PWR HOUSE | Apr 30 | May 14 | Apr 15 | Oct 10 | 162 |
| BIGFORK 13 S | May 1 | May 16 | Apr 16 | Oct 15 | 165 |
| GLASGOW #2 | May 3 | May 15 | Apr 19 | Oct 1 | 151 |
| GLENDIVE | May 3 | May 16 | Apr 19 | Oct 4 | 153 |
| BILLINGS LOGAN INTL AP | May 4 | May 18 | Apr 20 | Oct 7 | 156 |
| BILLINGS WFO | May 5 | May 21 | Apr 23 | Oct 3 | 149 |
| MOSBY 4 ENE | May 5 | May 26 | Apr 20 | Oct 4 | 151 |
| GLASGOW INTL AP | May 6 | May 18 | Apr 24 | Sep 30 | 145 |
| GREAT FALLS 16ST | May 6 | May 19 | Apr 23 | Oct 1 | 147 |
| MISSOULA 6 NW WFO | May 6 | May 19 | Apr 24 | Oct 4 | 151 |
| HIGHWOOD 7 NE | May 7 | May 21 | Apr 24 | Oct 2 | 149 |
| MALTA 7 E | May 7 | May 21 | Apr 24 | Sep 28 | 143 |
| THOMPSON FALLS PH | May 7 | May 19 | Apr 25 | Oct 4 | 150 |
| YELLOWTAIL DAM | May 7 | May 24 | Apr 20 | Oct 5 | 151 |
| FT PECK PWR PLT | May 8 | May 20 | Apr 25 | Oct 1 | 145 |
| MILES CITY F WILEY FLD | May 8 | May 21 | Apr 26 | Sep 30 | 144 |
| WOLF PT | May 8 | May 20 | Apr 25 | Sep 28 | 143 |
| FORSYTH | May 9 | May 21 | Apr 28 | Sep 29 | 142 |
| HELENA RGNL AP | May 9 | May 25 | Apr 29 | Sep 30 | 142 |
| HUNGRY HORSE DAM | May 9 | May 30 | Apr 25 | Oct 1 | 141 |
| TRIDENT | May 9 | May 24 | Apr 29 | Sep 27 | 139 |
| BILLINGS WTP | May 10 | May 24 | Apr 26 | Oct 1 | 142 |
| HYSHAM | May 10 | May 22 | Apr 28 | Sep 29 | 141 |
| LIBBY | May 10 | May 26 | Apr 28 | Sep 26 | 137 |
| MALTA | May 10 | May 22 | Apr 29 | Sep 29 | 139 |
| MELSTONE | May 10 | May 23 | Apr 28 | Sep 29 | 141 |
| MISSOULA 2 NE | May 10 | May 28 | Apr 27 | Oct 1 | 143 |
| POLSON | May 10 | May 26 | Apr 27 | Oct 5 | 147 |
| EUREKA RS | May 11 | May 25 | Apr 28 | Sep 27 | 138 |
| LIBBY DAM (BASE) | May 11 | May 27 | Apr 30 | Oct 1 | 142 |
| SIDNEY | May 11 | May 25 | Apr 30 | Sep 27 | 137 |
| BAKER | May 12 | May 27 | Apr 29 | Sep 26 | 135 |
| CRESTON | May 12 | May 26 | Apr 30 | Sep 25 | 134 |
| GREAT FALLS WFO | May 12 | May 27 | Apr 30 | Sep 28 | 138 |
| HUNTLEY EXP STN | May 12 | May 26 | Apr 30 | Sep 25 | 136 |
| NASHUA #2 | May 12 | May 26 | Apr 30 | Sep 24 | 134 |
| SAINT IGNATIUS | May 12 | Jun 1 | Apr 28 | Oct 2 | 142 |
| SAND CREEK | May 12 | May 27 | Apr 30 | Sep 27 | 136 |
| SAVAGE | May 12 | May 26 | May 1 | Sep 25 | 135 |
| TERRY | May 12 | May 25 | Apr 30 | Sep 28 | 137 |
| BRADY 27 ENE (THE KNEES) | May 13 | May 29 | Apr 30 | Sep 29 | 137 |
| FAIRFIELD | May 13 | Jun 1 | Apr 28 | Sep 27 | 135 |
| HARDIN | May 13 | May 26 | Apr 30 | Sep 29 | 135 |
| POWDERVILLE 8 NNE | May 13 | May 31 | May 1 | Sep 25 | 132 |
| ST MARIE | May 13 | May 26 | May 2 | Sep 27 | 134 |
| WOLF POINT 34 NE | May 13 | May 25 | Apr 30 | Sep 28 | 137 |
| BIDDLE 8 SW | May 14 | May 27 | May 2 | Sep 28 | 134 |
| BIG TIMBER | May 14 | May 27 | May 2 | Sep 26 | 133 |
| BRIDGER 2 N | May 14 | May 30 | May 2 | Sep 24 | 129 |
| CHINOOK | May 14 | May 27 | May 1 | Sep 23 | 130 |
| GERALDINE | May 14 | May 28 | May 2 | Sep 26 | 134 |
| LEWISTOWN | May 14 | May 27 | May 2 | Sep 28 | 135 |
| ROY 8 NE | May 14 | May 29 | May 3 | Sep 24 | 134 |
| TROY | May 14 | May 31 | Apr 29 | Sep 25 | 132 |
| COLSTRIP | May 15 | May 28 | May 2 | Sep 30 | 138 |
| FT ASSINIBOINE | May 15 | May 28 | May 4 | Sep 24 | 130 |
| FT BENTON | May 15 | May 30 | May 3 | Sep 22 | 129 |
| HAVRE CITY CO AP | May 15 | May 27 | May 3 | Sep 23 | 129 |
| HINSDALE 4 SW | May 15 | May 30 | May 3 | Sep 26 | 132 |
| ROCK SPRINGS | May 15 | May 27 | May 2 | Sep 25 | 132 |
| SACO 1 NNW | May 15 | May 26 | May 3 | Sep 23 | 130 |
| SKQ DAM | May 15 | Jun 1 | May 3 | Sep 28 | 134 |
| SWEETGRASS | May 15 | May 28 | May 3 | Sep 25 | 132 |
| BAKER MUNI AP | May 16 | May 29 | May 4 | Sep 26 | 132 |
| BROADUS | May 16 | May 29 | May 2 | Sep 28 | 135 |
| BYNUM 4 SSE | May 16 | May 28 | May 2 | Sep 27 | 133 |
| FLATWILLOW 4 ENE | May 16 | May 31 | May 3 | Sep 28 | 132 |
| FORTINE 1 N | May 16 | Jun 3 | May 3 | Sep 18 | 121 |
| FT BELKNAP 2 SW | May 16 | May 28 | May 6 | Sep 22 | 128 |
| HARLEM | May 16 | May 31 | May 4 | Sep 21 | 125 |
| MALTA 35 S | May 16 | May 29 | May 4 | Sep 23 | 128 |
| MEDICINE LAKE 3 SE | May 16 | May 30 | May 4 | Sep 18 | 125 |
| MISSOULA INTL AP | May 16 | Jun 1 | May 3 | Sep 26 | 130 |
| TIBER DAM | May 16 | May 30 | May 2 | Sep 23 | 129 |
| VIDA 6 NE | May 16 | May 31 | May 2 | Sep 22 | 129 |
| WHITEFISH | May 16 | Jun 6 | May 2 | Sep 25 | 129 |
| WINIFRED | May 16 | May 30 | May 5 | Sep 23 | 127 |
| WOLF POINT INTL AP | May 16 | May 29 | May 5 | Sep 20 | 125 |
| BIG SANDY | May 17 | Jun 4 | May 4 | Sep 25 | 128 |
| CIRCLE | May 17 | May 31 | May 4 | Sep 22 | 126 |
| MOORHEAD 9 NE | May 17 | May 31 | May 5 | Sep 22 | 126 |
| RIDGEWAY 1 S | May 17 | Jun 1 | May 5 | Sep 22 | 127 |
| RYEGATE | May 17 | May 30 | May 3 | Sep 23 | 127 |
| SUNBURST 8 E | May 17 | May 31 | May 2 | Sep 25 | 129 |
| SUPERIOR | May 17 | Jun 8 | May 1 | Sep 23 | 125 |
| SWAN LAKE | May 17 | Jun 4 | May 4 | Sep 19 | 121 |
| VALIER | May 17 | May 31 | May 3 | Sep 24 | 129 |
| ALBERTON | May 18 | Jun 6 | May 5 | Sep 25 | 126 |
| BRANDENBERG | May 18 | May 30 | May 6 | Sep 22 | 126 |
| CARLYLE 13 NW | May 18 | May 31 | May 4 | Sep 29 | 134 |
| JORDAN AP | May 18 | May 31 | May 6 | Sep 20 | 123 |
| VALENTINE | May 18 | May 31 | May 7 | Sep 21 | 124 |
| W GLACIER | May 18 | Jun 4 | May 6 | Sep 20 | 124 |
| WESTBY | May 18 | May 30 | May 6 | Sep 21 | 125 |
| ZORTMAN | May 18 | Jun 1 | May 4 | Sep 23 | 126 |
| AUGUSTA | May 19 | May 31 | May 4 | Sep 21 | 125 |
| GREAT FALLS INTL AP | May 19 | Jun 2 | May 7 | Sep 24 | 126 |
| HOLTER DAM | May 19 | Jun 8 | May 6 | Sep 24 | 124 |
| LEWISTOWN 11ESE | May 19 | Jun 1 | May 7 | Sep 25 | 128 |
| LIVINGSTON 12 S | May 19 | Jun 11 | May 5 | Sep 25 | 125 |
| PORT OF MORGAN | May 19 | Jun 2 | May 5 | Sep 22 | 124 |
| RAYMOND BORDER STN | May 19 | Jun 1 | May 6 | Sep 23 | 125 |
| TOWNSEND 3SE | May 19 | Jun 2 | May 8 | Sep 19 | 122 |
| TURNER 11N | May 19 | Jun 1 | May 7 | Sep 21 | 124 |
| BREDETTE | May 20 | Jun 1 | May 8 | Sep 21 | 122 |
| BROCKWAY 3 WSW | May 20 | Jun 5 | May 6 | Sep 19 | 121 |
| CHOTEAU 8NE | May 20 | Jun 4 | May 7 | Sep 22 | 123 |
| CONRAD | May 20 | Jun 3 | May 9 | Sep 19 | 119 |
| EKALAKA | May 20 | Jun 1 | May 7 | Sep 23 | 126 |
| GRASS RANGE | May 20 | Jun 6 | May 6 | Sep 24 | 126 |
| HERON 2 NW | May 20 | Jun 5 | May 4 | Sep 20 | 119 |
| LINDBERGH LAKE | May 20 | Jun 7 | May 7 | Sep 22 | 120 |
| LOMA | May 20 | Jun 3 | May 8 | Sep 19 | 120 |
| MILDRED 5 N | May 20 | Jun 2 | May 6 | Sep 22 | 124 |
| ROUNDUP | May 20 | Jun 2 | May 6 | Sep 21 | 124 |
| TROUT CREEK RS | May 20 | Jun 9 | May 5 | Sep 21 | 122 |
| CASCADE 5 S | May 21 | Jun 6 | May 5 | Sep 19 | 120 |
| CULBERTSON | May 21 | Jun 3 | May 8 | Sep 20 | 120 |
| GARDINER | May 21 | Jun 9 | May 5 | Sep 27 | 128 |
| HAMILTON | May 21 | Jun 6 | May 7 | Sep 22 | 122 |
| INGOMAR 9 E | May 21 | Jun 4 | May 8 | Sep 19 | 120 |
| JOPLIN | May 21 | Jun 6 | May 8 | Sep 19 | 119 |
| JORDAN | May 21 | Jun 2 | May 8 | Sep 18 | 118 |
| PLEVNA | May 21 | Jun 4 | May 9 | Sep 20 | 121 |
| ROGERS PASS 9 NNE | May 21 | Jun 8 | May 7 | Sep 15 | 115 |
| WYOLA 1 SW | May 21 | Jun 2 | May 9 | Sep 17 | 117 |
| MIZPAH 4 NNW | May 22 | Jun 7 | May 9 | Sep 15 | 117 |
| POMPEYS PILLAR 15N | May 22 | Jun 7 | May 9 | Sep 22 | 121 |
| RAYNESFORD 2 NNW | May 22 | Jun 9 | May 7 | Sep 23 | 123 |
| ROUNDUP 15 SW | May 22 | Jun 4 | May 11 | Sep 15 | 114 |
| STEVENSVILLE | May 22 | Jun 13 | May 7 | Sep 19 | 115 |
| BOZEMAN 6 W EXP FARM | May 23 | Jun 12 | May 5 | Sep 23 | 123 |
| BUSBY | May 23 | Jun 7 | May 12 | Sep 15 | 113 |
| CARTER 14 W | May 23 | Jun 9 | May 10 | Sep 23 | 120 |
| CHINOOK 35SE | May 23 | Jun 3 | May 11 | Sep 23 | 121 |
| DUNKIRK 19NNE | May 23 | Jun 8 | May 12 | Sep 14 | 112 |
| HARLOWTON | May 23 | Jun 6 | May 12 | Sep 16 | 113 |
| LEWISTOWN MUNI AP | May 23 | Jun 8 | May 11 | Sep 21 | 119 |
| LIBBY 1 NE RS | May 23 | Jun 7 | May 9 | Sep 21 | 120 |
| RUDYARD 19S | May 23 | Jun 3 | May 12 | Sep 19 | 119 |
| SHELBY | May 23 | Jun 6 | May 11 | Sep 16 | 115 |
| WESTERN AG RSCH CTR | May 23 | Jun 10 | May 8 | Sep 21 | 118 |
| CHESTER | May 24 | Jun 9 | May 11 | Sep 17 | 115 |
| CUT BANK MUNI AP | May 24 | Jun 5 | May 11 | Sep 15 | 113 |
| DARBY | May 24 | Jun 14 | May 6 | Sep 23 | 118 |
| GILDFORD | May 24 | Jun 7 | May 12 | Sep 15 | 114 |
| HARLEM 20S | May 24 | Jun 11 | May 12 | Sep 22 | 118 |
| LAURIN 2NE | May 24 | Jun 13 | May 11 | Sep 22 | 117 |
| RAPELJE | May 24 | Jun 11 | May 11 | Sep 21 | 116 |
| SHONKIN 7 S | May 24 | Jun 10 | May 6 | Sep 21 | 119 |
| WOLF POINT 29 ENE | May 24 | Jun 6 | May 12 | Sep 14 | 110 |
| COHAGEN | May 25 | Jun 9 | May 12 | Sep 14 | 110 |
| CONTENT 4 NNE | May 25 | Jun 8 | May 11 | Sep 14 | 110 |
| PLENTYWOOD | May 25 | Jun 8 | May 13 | Sep 14 | 111 |
| SONNETTE 7 SW | May 25 | Jun 7 | May 12 | Sep 19 | 115 |
| STANFORD | May 25 | Jun 15 | May 10 | Sep 21 | 118 |
| BOZEMAN GALLATIN FLD | May 26 | Jun 12 | May 11 | Sep 16 | 112 |
| BOZEMAN MONTANA STATE UNIV | May 26 | Jun 14 | May 9 | Sep 22 | 116 |
| HYSHAM 25 SSE | May 26 | Jun 13 | May 12 | Sep 16 | 111 |
| LOGAN LANDFILL | May 26 | Jun 12 | May 11 | Sep 15 | 111 |
| RYEGATE 18 NNW | May 26 | Jun 13 | May 12 | Sep 18 | 112 |
| SIMPSON 6 N - WILDHORSE | May 26 | Jun 8 | May 12 | Sep 15 | 110 |
| TERRY 21 NNW | May 26 | Jun 13 | May 13 | Sep 17 | 113 |
| COLUMBUS | May 27 | Jun 12 | May 14 | Sep 14 | 108 |
| GIBSON 2 NE | May 27 | Jun 12 | May 12 | Sep 18 | 113 |
| LIVINGSTON MISSION FLD | May 27 | Jun 14 | May 13 | Sep 14 | 108 |
| WIBAUX 2 E | May 27 | Jun 13 | May 15 | Sep 16 | 112 |
| CHOTEAU | May 28 | Jun 20 | May 15 | Sep 12 | 104 |
| DEL BONITA | May 28 | Jun 12 | May 12 | Sep 16 | 110 |
| MOCCASIN EXP STN | May 28 | Jun 19 | May 13 | Sep 20 | 112 |
| REDSTONE | May 28 | Jun 13 | May 15 | Sep 7 | 101 |
| SCOBEY 4 NW | May 28 | Jun 13 | May 16 | Sep 6 | 99 |
| JOLIET | May 29 | Jun 17 | May 14 | Sep 15 | 107 |
| HARLOWTON 11NW | May 30 | Jun 17 | May 16 | Sep 20 | 110 |
| RUDYARD 21 N | May 30 | Jun 15 | May 17 | Sep 11 | 103 |
| KALISPELL GLACIER AP | May 31 | Jun 22 | May 13 | Sep 10 | 100 |
| LEWISTOWN 11 SSE | May 31 | Jun 18 | May 16 | Sep 14 | 105 |
| ANACONDA | Jun 1 | Jun 25 | May 14 | Sep 14 | 105 |
| DENTON | Jun 1 | Jun 26 | May 15 | Sep 11 | 101 |
| JUDITH GAP | Jun 1 | Jun 16 | May 17 | Sep 15 | 104 |
| NYE #2 | Jun 1 | Jun 21 | May 15 | Sep 11 | 100 |
| OPHEIM 10 N | Jun 1 | Jun 18 | May 20 | Sep 7 | 99 |
| ALBION 1 N | Jun 2 | Jun 21 | May 18 | Sep 6 | 95 |
| DILLON AP | Jun 2 | Jun 21 | May 17 | Sep 13 | 101 |
| SUN RVR 4 S | Jun 2 | Jun 21 | May 18 | Sep 10 | 96 |
| JUDITH GAP 13 E | Jun 3 | Jun 25 | May 19 | Sep 15 | 100 |
| MARTINSDALE 3 NNW | Jun 3 | Jun 25 | May 20 | Sep 8 | 94 |
| RED LODGE | Jun 3 | Jun 18 | May 19 | Sep 19 | 106 |
| ST. MARY 1 SSW | Jun 3 | Jun 23 | May 19 | Sep 8 | 94 |
| ADEL | Jun 4 | Jun 22 | May 22 | Sep 12 | 98 |
| AUSTIN 1 W | Jun 4 | Jun 18 | May 18 | Sep 14 | 100 |
| VIRGINIA CITY | Jun 4 | Jun 23 | May 17 | Sep 18 | 106 |
| WHITE SULPHUR SPRINGS #2 | Jun 4 | Jun 20 | May 21 | Sep 11 | 97 |
| WILSALL 1S | Jun 4 | Jun 23 | May 19 | Sep 6 | 92 |
| DILLON U OF MONTANA WESTERN | Jun 5 | Jun 23 | May 18 | Sep 13 | 98 |
| MYSTIC LAKE | Jun 5 | Jun 21 | May 22 | Sep 14 | 99 |
| OPHEIM 12 SSE | Jun 5 | Jun 23 | May 22 | Sep 2 | 89 |
| ALDER 17 S | Jun 6 | Jun 25 | May 20 | Sep 14 | 98 |
| NEIHART 8 NNW | Jun 6 | Jun 28 | May 23 | Sep 12 | 99 |
| BOULDER | Jun 7 | Jun 25 | May 24 | Sep 8 | 90 |
| E GLACIER | Jun 8 | Jul 1 | May 24 | Sep 5 | 88 |
| TWIN BRIDGES | Jun 8 | Jul 1 | May 22 | Sep 2 | 82 |
| WILSALL 8 ENE | Jun 8 | Jun 30 | May 23 | Sep 7 | 89 |
| BLACKLEAF | Jun 9 | Jul 2 | May 25 | Sep 3 | 86 |
| ELLISTON | Jun 9 | Jun 26 | May 23 | Sep 8 | 91 |
| MELVILLE 4 W | Jun 9 | Jun 27 | May 26 | Sep 7 | 88 |
| DIVIDE | Jun 10 | Jul 2 | May 23 | Sep 7 | 85 |
| LIMA | Jun 11 | Jun 30 | May 24 | Sep 10 | 89 |
| MILLEGAN 14 SE | Jun 11 | Jul 3 | May 27 | Sep 6 | 86 |
| GIBSON DAM | Jun 12 | Jul 5 | May 25 | Sep 8 | 88 |
| ST MARY | Jun 12 | Jul 3 | May 27 | Sep 5 | 82 |
| BUTTE BERT MOONEY AP | Jun 13 | Jul 1 | May 27 | Sep 5 | 83 |
| HEBGEN DAM | Jun 15 | Jul 7 | May 29 | Sep 10 | 87 |
| LEWISTOWN 42 WSW | Jun 15 | Jul 8 | May 31 | Sep 4 | 77 |
| ENNIS | Jun 16 | Jul 6 | May 30 | Sep 4 | 78 |
| TIZER GARDENS | Jun 18 | Jul 3 | May 30 | Sep 5 | 81 |
How to read the three dates
Average is the date by which, in half of the years between 1991 and 2020, the last 32 °F night had already happened. Safe is later: only one year in ten saw a frost after it, which is the date to set out frost-tender plants such as dahlia tubers and zinnia seedlings. Early is the risky end, with a frost after it in nine years out of ten.
Every figure is for the weather station, not for your garden. A valley bottom, a north slope or a spot near a lake can run a week or two either way. Cities are warmer than the countryside around them.
Where the numbers come from
The dates are NOAA's U.S. Climate Normals for 1991 to 2020, computed by the National Centers for Environmental Information for every station with thirty years of daily minimum temperatures. ZIP codes are matched to the nearest such station within 150 km using U.S. Census Bureau ZIP Code Tabulation Area centroids. Stations that never see a frost, such as much of south Florida, report no date and are left out.