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Montana frost dates

Across 216 NOAA climate stations in Montana, the median last spring frost (32°F) ranges from Apr 30 at Norris Madison Pwr House to Jun 18 at Tizer Gardens; the typical station sees its last frost around May 20 and its first fall frost around Sep 22.

“Median” dates have a 50% chance of a later spring frost or an earlier fall frost. “10% risk” dates are the safer choice for tender plants: only 1 year in 10 has frost beyond them. Source: NOAA NCEI 1991–2020 Climate Normals. Elevation matters: within a state, frost dates can differ by a month or more between valleys and hills.

StationElevationLast frost (median)Last frost (10% risk)First frost (median)First frost (10% risk)Growing season
Adel5,017 ftJun 4Jun 22Sep 12Aug 2698 days
Alberton3,060 ftMay 18Jun 6Sep 25Sep 7126 days
Albion 1 N3,312 ftJun 2Jun 21Sep 6Aug 2395 days
Alder 17 S5,850 ftJun 6Jun 25Sep 14Aug 3198 days
Anaconda5,230 ftJun 1Jun 25Sep 14Aug 31105 days
Augusta4,070 ftMay 19May 31Sep 21Sep 4125 days
Austin 1 W4,851 ftJun 4Jun 18Sep 14Aug 30100 days
Baker2,933 ftMay 12May 27Sep 26Sep 11135 days
Baker Muni AP2,971 ftMay 16May 29Sep 26Sep 11132 days
Biddle 8 Sw3,631 ftMay 14May 27Sep 28Sep 13134 days
Big Sandy2,770 ftMay 17Jun 4Sep 25Sep 12128 days
Big Timber4,100 ftMay 14May 27Sep 26Sep 10133 days
Bigfork 13 S2,979 ftMay 1May 16Oct 15Sep 30165 days
Billings Logan Intl AP3,581 ftMay 4May 18Oct 7Sep 26156 days
Billings Wfo3,185 ftMay 5May 21Oct 3Sep 20149 days
Billings Wtp3,097 ftMay 10May 24Oct 1Sep 19142 days
Blackleaf4,235 ftJun 9Jul 2Sep 3Aug 1986 days
Boulder4,904 ftJun 7Jun 25Sep 8Aug 2590 days
Bozeman 6 W Exp Farm4,775 ftMay 23Jun 12Sep 23Sep 4123 days
Bozeman Gallatin Fld4,427 ftMay 26Jun 12Sep 16Sep 2112 days
Bozeman Montana State Univ4,913 ftMay 26Jun 14Sep 22Sep 5116 days
Brady 27 Ene (The Knees)3,325 ftMay 13May 29Sep 29Sep 16137 days
Brandenberg2,770 ftMay 18May 30Sep 22Sep 8126 days
Bredette2,313 ftMay 20Jun 1Sep 21Sep 6122 days
Bridger 2 N3,583 ftMay 14May 30Sep 24Sep 7129 days
Broadus3,032 ftMay 16May 29Sep 28Sep 13135 days
Brockway 3 Wsw2,630 ftMay 20Jun 5Sep 19Sep 4121 days
Busby3,430 ftMay 23Jun 7Sep 15Sep 1113 days
Butte Bert Mooney AP5,506 ftJun 13Jul 1Sep 5Aug 2483 days
Bynum 4 Sse4,039 ftMay 16May 28Sep 27Sep 16133 days
Carlyle 13 Nw3,145 ftMay 18May 31Sep 29Sep 13134 days
Carter 14 W3,450 ftMay 23Jun 9Sep 23Sep 8120 days
Cascade 5 S3,360 ftMay 21Jun 6Sep 19Sep 2120 days
Chester3,132 ftMay 24Jun 9Sep 17Sep 3115 days
Chinook2,420 ftMay 14May 27Sep 23Sep 11130 days
Chinook 35SE3,360 ftMay 23Jun 3Sep 23Sep 11121 days
Choteau3,845 ftMay 28Jun 20Sep 12Aug 30104 days
Choteau 8NE3,741 ftMay 20Jun 4Sep 22Sep 8123 days
Circle2,480 ftMay 17May 31Sep 22Sep 7126 days
Cohagen2,720 ftMay 25Jun 9Sep 14Aug 31110 days
Colstrip3,218 ftMay 15May 28Sep 30Sep 15138 days
Columbus3,602 ftMay 27Jun 12Sep 14Sep 1108 days
Conrad3,550 ftMay 20Jun 3Sep 19Sep 4119 days
Content 4 Nne2,325 ftMay 25Jun 8Sep 14Aug 29110 days
Creston2,935 ftMay 12May 26Sep 25Sep 9134 days
Culbertson1,940 ftMay 21Jun 3Sep 20Sep 6120 days
Cut Bank Muni AP3,838 ftMay 24Jun 5Sep 15Sep 1113 days
Darby3,880 ftMay 24Jun 14Sep 23Sep 4118 days
Del Bonita4,337 ftMay 28Jun 12Sep 16Aug 28110 days
Denton3,610 ftJun 1Jun 26Sep 11Aug 29101 days
Dillon AP5,200 ftJun 2Jun 21Sep 13Aug 30101 days
Dillon U Of Montana Western5,129 ftJun 5Jun 23Sep 13Aug 2998 days
Divide5,350 ftJun 10Jul 2Sep 7Aug 2485 days
Dunkirk 19NNE3,323 ftMay 23Jun 8Sep 14Sep 1112 days
E Glacier4,806 ftJun 8Jul 1Sep 5Aug 2088 days
Ekalaka3,432 ftMay 20Jun 1Sep 23Sep 7126 days
Elliston5,080 ftJun 9Jun 26Sep 8Aug 2691 days
Ennis4,953 ftJun 16Jul 6Sep 4Aug 2078 days
Eureka Rs2,532 ftMay 11May 25Sep 27Sep 10138 days
Fairfield3,983 ftMay 13Jun 1Sep 27Sep 14135 days
Flatwillow 4 Ene3,292 ftMay 16May 31Sep 28Sep 15132 days
Forsyth2,515 ftMay 9May 21Sep 29Sep 16142 days
Fortine 1 N3,000 ftMay 16Jun 3Sep 18Sep 1121 days
Ft Assiniboine2,675 ftMay 15May 28Sep 24Sep 8130 days
Ft Belknap 2 Sw2,527 ftMay 16May 28Sep 22Sep 10128 days
Ft Benton2,649 ftMay 15May 30Sep 22Sep 7129 days
Ft Peck Pwr Plt2,071 ftMay 8May 20Oct 1Sep 18145 days
Gardiner5,275 ftMay 21Jun 9Sep 27Sep 12128 days
Geraldine3,145 ftMay 14May 28Sep 26Sep 13134 days
Gibson 2 Ne4,444 ftMay 27Jun 12Sep 18Sep 3113 days
Gibson Dam4,590 ftJun 12Jul 5Sep 8Aug 2388 days
Gildford2,820 ftMay 24Jun 7Sep 15Aug 29114 days
Glasgow #22,090 ftMay 3May 15Oct 1Sep 19151 days
Glasgow Intl AP2,285 ftMay 6May 18Sep 30Sep 17145 days
Glendive2,075 ftMay 3May 16Oct 4Sep 22153 days
Grass Range3,490 ftMay 20Jun 6Sep 24Sep 11126 days
Great Falls 16st3,505 ftMay 6May 19Oct 1Sep 17147 days
Great Falls Intl AP3,664 ftMay 19Jun 2Sep 24Sep 9126 days
Great Falls Wfo3,705 ftMay 12May 27Sep 28Sep 14138 days
Hamilton3,585 ftMay 21Jun 6Sep 22Sep 6122 days
Hardin2,880 ftMay 13May 26Sep 29Sep 14135 days
Harlem2,371 ftMay 16May 31Sep 21Sep 8125 days
Harlem 20S2,695 ftMay 24Jun 11Sep 22Sep 8118 days
Harlowton4,222 ftMay 23Jun 6Sep 16Sep 1113 days
Harlowton 11NW4,954 ftMay 30Jun 17Sep 20Sep 4110 days
Havre City Co AP2,585 ftMay 15May 27Sep 23Sep 11129 days
Hebgen Dam6,489 ftJun 15Jul 7Sep 10Aug 2587 days
Helena Rgnl AP3,828 ftMay 9May 25Sep 30Sep 17142 days
Heron 2 Nw2,240 ftMay 20Jun 5Sep 20Sep 1119 days
Highwood 7 Ne3,600 ftMay 7May 21Oct 2Sep 19149 days
Hinsdale 4 Sw2,805 ftMay 15May 30Sep 26Sep 12132 days
Holter Dam3,487 ftMay 19Jun 8Sep 24Sep 6124 days
Hungry Horse Dam3,160 ftMay 9May 30Oct 1Sep 13141 days
Huntley Exp Stn3,034 ftMay 12May 26Sep 25Sep 13136 days
Hysham2,669 ftMay 10May 22Sep 29Sep 15141 days
Hysham 25 Sse3,100 ftMay 26Jun 13Sep 16Sep 1111 days
Ingomar 9 E2,800 ftMay 21Jun 4Sep 19Sep 6120 days
Joliet3,838 ftMay 29Jun 17Sep 15Sep 1107 days
Joplin3,323 ftMay 21Jun 6Sep 19Sep 3119 days
Jordan2,620 ftMay 21Jun 2Sep 18Sep 4118 days
Jordan AP2,662 ftMay 18May 31Sep 20Sep 8123 days
Judith Gap4,630 ftJun 1Jun 16Sep 15Aug 31104 days
Judith Gap 13 E4,791 ftJun 3Jun 25Sep 15Aug 29100 days
Kalispell Glacier AP2,957 ftMay 31Jun 22Sep 10Aug 26100 days
Laurin 2NE5,198 ftMay 24Jun 13Sep 22Sep 6117 days
Lewistown3,911 ftMay 14May 27Sep 28Sep 14135 days
Lewistown 11 Sse4,965 ftMay 31Jun 18Sep 14Aug 30105 days
Lewistown 11ESE5,028 ftMay 19Jun 1Sep 25Sep 11128 days
Lewistown 42 Wsw5,070 ftJun 15Jul 8Sep 4Aug 1977 days
Lewistown Muni AP4,145 ftMay 23Jun 8Sep 21Sep 8119 days
Libby2,140 ftMay 10May 26Sep 26Sep 11137 days
Libby 1 Ne Rs2,096 ftMay 23Jun 7Sep 21Sep 3120 days
Libby Dam (Base)2,110 ftMay 11May 27Oct 1Sep 14142 days
Lima6,279 ftJun 11Jun 30Sep 10Aug 2789 days
Lindbergh Lake4,320 ftMay 20Jun 7Sep 22Sep 5120 days
Livingston 12 S5,044 ftMay 19Jun 11Sep 25Sep 7125 days
Livingston Mission Fld4,643 ftMay 27Jun 14Sep 14Aug 27108 days
Logan Landfill4,243 ftMay 26Jun 12Sep 15Sep 1111 days
Loma2,578 ftMay 20Jun 3Sep 19Sep 4120 days
Malta2,262 ftMay 10May 22Sep 29Sep 17139 days
Malta 35 S2,615 ftMay 16May 29Sep 23Sep 10128 days
Malta 7 E2,231 ftMay 7May 21Sep 28Sep 14143 days
Martinsdale 3 Nnw4,800 ftJun 3Jun 25Sep 8Aug 2394 days
Medicine Lake 3 Se1,942 ftMay 16May 30Sep 18Sep 7125 days
Melstone2,932 ftMay 10May 23Sep 29Sep 14141 days
Melville 4 W5,365 ftJun 9Jun 27Sep 7Aug 2188 days
Mildred 5 N2,482 ftMay 20Jun 2Sep 22Sep 7124 days
Miles City F Wiley Fld2,624 ftMay 8May 21Sep 30Sep 17144 days
Millegan 14 Se4,970 ftJun 11Jul 3Sep 6Aug 2086 days
Missoula 2 Ne3,420 ftMay 10May 28Oct 1Sep 16143 days
Missoula 6 Nw Wfo3,197 ftMay 6May 19Oct 4Sep 23151 days
Missoula Intl AP3,192 ftMay 16Jun 1Sep 26Sep 12130 days
Mizpah 4 Nnw2,480 ftMay 22Jun 7Sep 15Sep 2117 days
Moccasin Exp Stn4,300 ftMay 28Jun 19Sep 20Sep 4112 days
Moorhead 9 Ne3,220 ftMay 17May 31Sep 22Sep 7126 days
Mosby 4 Ene2,910 ftMay 5May 26Oct 4Sep 22151 days
Mystic Lake6,544 ftJun 5Jun 21Sep 14Aug 3199 days
Nashua #22,067 ftMay 12May 26Sep 24Sep 12134 days
Neihart 8 Nnw5,230 ftJun 6Jun 28Sep 12Aug 2999 days
Norris Madison Pwr House4,745 ftApr 30May 14Oct 10Sep 27162 days
Nye #24,840 ftJun 1Jun 21Sep 11Aug 25100 days
Opheim 10 N2,878 ftJun 1Jun 18Sep 7Aug 2499 days
Opheim 12 Sse2,936 ftJun 5Jun 23Sep 2Aug 1589 days
Plentywood2,048 ftMay 25Jun 8Sep 14Sep 2111 days
Plevna2,780 ftMay 21Jun 4Sep 20Sep 5121 days
Polson3,010 ftMay 10May 26Oct 5Sep 22147 days
Pompeys Pillar 15N3,390 ftMay 22Jun 7Sep 22Sep 7121 days
Port Of Morgan2,830 ftMay 19Jun 2Sep 22Sep 9124 days
Powderville 8 Nne2,800 ftMay 13May 31Sep 25Sep 6132 days
Rapelje4,068 ftMay 24Jun 11Sep 21Sep 4116 days
Raymond Border Stn2,345 ftMay 19Jun 1Sep 23Sep 11125 days
Raynesford 2 Nnw4,215 ftMay 22Jun 9Sep 23Sep 7123 days
Red Lodge5,646 ftJun 3Jun 18Sep 19Aug 31106 days
Redstone2,106 ftMay 28Jun 13Sep 7Aug 22101 days
Ridgeway 1 S3,316 ftMay 17Jun 1Sep 22Sep 5127 days
Rock Springs3,024 ftMay 15May 27Sep 25Sep 10132 days
Rogers Pass 9 Nne4,200 ftMay 21Jun 8Sep 15Aug 30115 days
Roundup3,200 ftMay 20Jun 2Sep 21Sep 5124 days
Roundup 15 Sw3,386 ftMay 22Jun 4Sep 15Aug 31114 days
Roy 8 Ne3,085 ftMay 14May 29Sep 24Sep 12134 days
Rudyard 19S2,878 ftMay 23Jun 3Sep 19Sep 5119 days
Rudyard 21 N3,000 ftMay 30Jun 15Sep 11Aug 27103 days
Ryegate3,650 ftMay 17May 30Sep 23Sep 10127 days
Ryegate 18 Nnw4,440 ftMay 26Jun 13Sep 18Sep 1112 days
Saco 1 Nnw2,185 ftMay 15May 26Sep 23Sep 11130 days
Saint Ignatius2,915 ftMay 12Jun 1Oct 2Sep 19142 days
Sand Creek2,910 ftMay 12May 27Sep 27Sep 14136 days
Savage1,978 ftMay 12May 26Sep 25Sep 12135 days
Scobey 4 Nw2,390 ftMay 28Jun 13Sep 6Aug 2499 days
Shelby3,325 ftMay 23Jun 6Sep 16Sep 3115 days
Shonkin 7 S4,300 ftMay 24Jun 10Sep 21Aug 31119 days
Sidney1,933 ftMay 11May 25Sep 27Sep 13137 days
Simpson 6 N - Wildhorse2,815 ftMay 26Jun 8Sep 15Sep 1110 days
Skq Dam2,730 ftMay 15Jun 1Sep 28Sep 13134 days
Sonnette 7 Sw3,914 ftMay 25Jun 7Sep 19Sep 1115 days
St Marie2,756 ftMay 13May 26Sep 27Sep 13134 days
St Mary4,560 ftJun 12Jul 3Sep 5Aug 1882 days
St. Mary 1 Ssw4,555 ftJun 3Jun 23Sep 8Aug 2294 days
Stanford4,860 ftMay 25Jun 15Sep 21Sep 6118 days
Stevensville3,375 ftMay 22Jun 13Sep 19Sep 3115 days
Sun Rvr 4 S3,600 ftJun 2Jun 21Sep 10Aug 2596 days
Sunburst 8 E3,700 ftMay 17May 31Sep 25Sep 9129 days
Superior2,710 ftMay 17Jun 8Sep 23Sep 6125 days
Swan Lake3,100 ftMay 17Jun 4Sep 19Sep 4121 days
Sweetgrass3,510 ftMay 15May 28Sep 25Sep 11132 days
Terry2,250 ftMay 12May 25Sep 28Sep 13137 days
Terry 21 Nnw3,142 ftMay 26Jun 13Sep 17Sep 1113 days
Thompson Falls Ph2,380 ftMay 7May 19Oct 4Sep 21150 days
Tiber Dam2,850 ftMay 16May 30Sep 23Sep 9129 days
Tizer Gardens4,672 ftJun 18Jul 3Sep 5Aug 2181 days
Townsend 3SE3,964 ftMay 19Jun 2Sep 19Sep 5122 days
Trident4,036 ftMay 9May 24Sep 27Sep 12139 days
Trout Creek Rs2,356 ftMay 20Jun 9Sep 21Sep 2122 days
Troy1,929 ftMay 14May 31Sep 25Sep 9132 days
Turner 11N2,982 ftMay 19Jun 1Sep 21Sep 8124 days
Twin Bridges4,625 ftJun 8Jul 1Sep 2Aug 1682 days
Valentine2,905 ftMay 18May 31Sep 21Sep 7124 days
Valier3,807 ftMay 17May 31Sep 24Sep 11129 days
Vida 6 Ne2,284 ftMay 16May 31Sep 22Sep 10129 days
Virginia City5,773 ftJun 4Jun 23Sep 18Sep 3106 days
W Glacier3,148 ftMay 18Jun 4Sep 20Sep 3124 days
Westby2,103 ftMay 18May 30Sep 21Sep 7125 days
Western Ag Rsch Ctr3,608 ftMay 23Jun 10Sep 21Sep 5118 days
White Sulphur Springs #25,040 ftJun 4Jun 20Sep 11Aug 2797 days
Whitefish3,100 ftMay 16Jun 6Sep 25Sep 8129 days
Wibaux 2 E2,696 ftMay 27Jun 13Sep 16Sep 2112 days
Wilsall 1S5,015 ftJun 4Jun 23Sep 6Aug 2892 days
Wilsall 8 Ene5,865 ftJun 8Jun 30Sep 7Aug 2189 days
Winifred3,243 ftMay 16May 30Sep 23Sep 9127 days
Wolf Point 29 Ene2,085 ftMay 24Jun 6Sep 14Sep 1110 days
Wolf Point 34 Ne2,643 ftMay 13May 25Sep 28Sep 14137 days
Wolf Point Intl AP1,986 ftMay 16May 29Sep 20Sep 7125 days
Wolf Pt2,090 ftMay 8May 20Sep 28Sep 15143 days
Wyola 1 Sw3,730 ftMay 21Jun 2Sep 17Sep 5117 days
Yellowtail Dam3,305 ftMay 7May 24Oct 5Sep 20151 days
Zortman4,035 ftMay 18Jun 1Sep 23Sep 7126 days
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