Last frost dates in Idaho
127 NOAA weather stations in Idaho have thirty years of frost records. The median station sees its last 32 °F night around May 16; across the state that ranges from Apr 2 to Jun 22, so pick the station nearest you rather than a state-wide figure.
| BROWNLEE DAM | Apr 2 | Apr 20 | Mar 15 | Nov 5 | 216 |
| LEWISTON NEZ PERCE CO AP | Apr 6 | Apr 26 | Mar 20 | Oct 26 | 200 |
| SWAN FALLS PH | Apr 12 | May 6 | Mar 23 | Oct 26 | 193 |
| LOWELL THREE RIVERS | Apr 16 | May 4 | Mar 26 | Oct 25 | 191 |
| BRUNEAU | Apr 17 | May 7 | Mar 31 | Oct 17 | 181 |
| PAYETTE | Apr 19 | May 5 | Apr 1 | Oct 20 | 183 |
| DWORSHAK FISH HATCHERY | Apr 20 | May 5 | Apr 1 | Oct 20 | 182 |
| COEUR D'ALENE | Apr 22 | May 6 | Apr 4 | Oct 18 | 179 |
| DEER FLAT DAM | Apr 23 | May 9 | Apr 5 | Oct 18 | 178 |
| WEISER | Apr 23 | May 10 | Apr 3 | Oct 13 | 174 |
| BOISE AIR TERMINAL | Apr 24 | May 9 | Apr 4 | Oct 21 | 179 |
| HOMEDALE 1 SE | Apr 24 | May 5 | Apr 9 | Oct 9 | 169 |
| SHOSHONE 1 WNW | Apr 24 | May 12 | Apr 9 | Oct 16 | 173 |
| BUHL #2 | Apr 25 | May 10 | Apr 8 | Oct 15 | 172 |
| FENN RS | Apr 26 | May 9 | Apr 8 | Oct 20 | 176 |
| PARMA EXP STN | Apr 27 | May 9 | Apr 13 | Oct 9 | 165 |
| ARROWROCK DAM | Apr 28 | May 16 | Apr 11 | Oct 14 | 169 |
| GRAND VIEW 4 NW | Apr 28 | May 13 | Apr 12 | Oct 6 | 162 |
| KAMIAH | Apr 29 | May 12 | Apr 9 | Oct 5 | 163 |
| NAMPA SUGAR FACTORY | Apr 29 | May 18 | Apr 15 | Oct 13 | 164 |
| BOISE LUCKY PEAK DAM | Apr 30 | May 18 | Apr 11 | Oct 22 | 173 |
| BONNERS FERRY | Apr 30 | May 16 | Apr 16 | Oct 4 | 154 |
| EMMETT 2 E | Apr 30 | May 17 | Apr 17 | Oct 17 | 168 |
| KOOSKIA 5 SSE | Apr 30 | May 13 | Apr 14 | Oct 11 | 162 |
| TWIN FALLS-KMVT | Apr 30 | May 14 | Apr 17 | Oct 9 | 161 |
| GLENNS FERRY | May 1 | May 16 | Apr 14 | Oct 3 | 154 |
| JEROME CO AP | May 1 | May 16 | Apr 17 | Oct 14 | 165 |
| JEROME | May 2 | May 30 | Apr 15 | Oct 14 | 166 |
| MTN HOME | May 2 | May 23 | Apr 18 | Oct 8 | 157 |
| POCATELLO CITY | May 2 | May 18 | Apr 17 | Oct 11 | 161 |
| YELLOWPINE BAR | May 2 | May 14 | Apr 18 | Oct 10 | 159 |
| HAGERMAN 2 SW | May 3 | May 17 | Apr 19 | Oct 1 | 151 |
| SAINT MARIES | May 3 | May 18 | Apr 20 | Oct 4 | 152 |
| SHOUP | May 3 | May 21 | Apr 17 | Oct 8 | 157 |
| AMERICAN FALLS | May 4 | May 21 | Apr 20 | Oct 8 | 155 |
| PORTHILL 1 SW | May 4 | May 28 | Apr 20 | Sep 30 | 145 |
| BLACKFOOT FIRE DEPT | May 5 | May 22 | Apr 23 | Oct 3 | 149 |
| WALLACE | May 5 | May 21 | Apr 22 | Oct 2 | 149 |
| COTTONWOOD 2 WSW | May 6 | May 26 | Apr 22 | Oct 13 | 156 |
| PAUL 1ENE | May 6 | May 22 | Apr 23 | Oct 6 | 151 |
| RIGGINS | May 6 | May 26 | Apr 23 | Oct 9 | 155 |
| TWIN FALLS 6 E | May 6 | May 26 | Apr 22 | Oct 3 | 150 |
| BURLEY MUNI AP | May 7 | May 23 | Apr 23 | Oct 4 | 150 |
| HAZELTON | May 7 | May 26 | Apr 24 | Oct 5 | 149 |
| SANDPOINT EXP STN | May 8 | May 25 | Apr 23 | Sep 28 | 141 |
| CABINET GORGE | May 9 | May 25 | Apr 24 | Oct 8 | 153 |
| GRANGEVILLE | May 9 | May 27 | Apr 24 | Oct 3 | 146 |
| IDAHO FALLS - KIFI | May 9 | Jun 2 | Apr 27 | Oct 1 | 142 |
| RIGBY | May 9 | May 25 | Apr 27 | Oct 5 | 148 |
| TWIN FALLS SUN VLY RGNL AP | May 9 | May 28 | Apr 25 | Oct 4 | 147 |
| COUNCIL | May 10 | Jun 1 | Apr 25 | Oct 2 | 145 |
| PLUMMER 3 WSW | May 11 | Jun 4 | Apr 25 | Oct 5 | 143 |
| TAYLOR RCH | May 11 | Jun 1 | Apr 29 | Sep 30 | 140 |
| MULLAN | May 12 | Jun 19 | Apr 26 | Sep 30 | 138 |
| REXBURG BYU IDAHO | May 12 | Jun 2 | Apr 29 | Sep 24 | 132 |
| BELLEVUE | May 13 | Jun 3 | Apr 30 | Oct 2 | 139 |
| AMERICAN FALLS 6 NE | May 14 | Jun 4 | Apr 30 | Oct 2 | 138 |
| CHALLIS AP | May 14 | Jun 2 | May 2 | Sep 25 | 131 |
| KELLOGG | May 14 | Jun 3 | Apr 30 | Sep 26 | 131 |
| CAMBRIDGE | May 15 | Jun 4 | Apr 29 | Sep 27 | 134 |
| OAKLEY | May 15 | Jun 6 | Apr 30 | Oct 2 | 137 |
| POTLATCH 3 NNE | May 15 | Jun 2 | Apr 30 | Sep 21 | 126 |
| REXBURG MADISON CO AP | May 15 | Jun 3 | May 1 | Sep 23 | 129 |
| ELK RVR | May 16 | Jun 1 | May 2 | Sep 23 | 128 |
| MINIDOKA DAM | May 16 | Jun 5 | Apr 30 | Oct 1 | 136 |
| POCATELLO 2 NE | May 16 | Jun 6 | Apr 30 | Oct 2 | 137 |
| PRESTON | May 16 | Jun 4 | May 2 | Sep 28 | 133 |
| BOISE 7 N | May 17 | Jun 10 | Apr 27 | Oct 12 | 147 |
| CASTLEFORD 2 N | May 17 | Jun 5 | Apr 30 | Sep 29 | 132 |
| MURPHY 10 W | May 17 | Jun 6 | May 2 | Sep 30 | 134 |
| SAINT ANTHONY | May 17 | Jun 10 | May 4 | Sep 22 | 126 |
| SALMON-KSRA | May 17 | Jun 9 | May 3 | Sep 24 | 127 |
| DUBOIS EXP STN | May 18 | Jun 9 | May 3 | Sep 30 | 132 |
| LIFTON PUMPING STN | May 19 | Jun 5 | May 3 | Sep 21 | 123 |
| FT HALL 1 NNE | May 20 | Jun 12 | May 6 | Sep 20 | 119 |
| MASSACRE ROCKS SP | May 20 | Jun 9 | May 4 | Sep 26 | 125 |
| PRIEST RVR EXP STN | May 20 | Jun 4 | May 6 | Sep 13 | 114 |
| ABERDEEN EXP STN | May 21 | Jun 13 | May 4 | Sep 20 | 118 |
| ASHTON 1N | May 21 | Jun 13 | May 4 | Sep 21 | 121 |
| LAVA HOT SPRINGS | May 21 | Jun 11 | May 6 | Sep 21 | 118 |
| MIDDLE FORK LODGE | May 21 | Jun 13 | May 7 | Sep 18 | 115 |
| REYNOLDS | May 21 | Jun 12 | May 4 | Sep 28 | 126 |
| ARCO | May 22 | Jun 9 | May 5 | Sep 22 | 119 |
| BAYVIEW MODEL BASIN | May 22 | Jun 6 | May 5 | Sep 22 | 122 |
| MALAD CITY | May 22 | Jun 16 | May 6 | Sep 20 | 116 |
| IDAHO FALLS FANNING FLD | May 23 | Jun 13 | May 7 | Sep 20 | 114 |
| MCCAMMON | May 23 | Jun 10 | May 6 | Sep 24 | 121 |
| POCATELLO RGNL AP | May 23 | Jun 13 | May 6 | Sep 18 | 117 |
| WINCHESTER | May 23 | Jun 19 | May 4 | Sep 25 | 121 |
| ARCO 17 SW | May 24 | Jun 15 | May 4 | Oct 1 | 130 |
| HOWE | May 24 | Jun 14 | May 6 | Sep 14 | 113 |
| NEZPERCE | May 24 | Jun 19 | May 6 | Sep 20 | 116 |
| RICHFIELD | May 24 | Jun 14 | May 6 | Sep 26 | 123 |
| GRACE | May 29 | Jun 16 | May 11 | Sep 17 | 111 |
| SUGAR CITY | May 29 | Jun 18 | May 12 | Sep 13 | 106 |
| CASCADE 1 NW | May 30 | Jun 21 | May 10 | Sep 19 | 110 |
| DOWNEY | May 31 | Jun 16 | May 13 | Sep 18 | 110 |
| OLA | May 31 | Jun 19 | May 8 | Sep 16 | 108 |
| POWELL | May 31 | Jun 26 | May 14 | Sep 12 | 102 |
| PRICHARD 3 ESE | May 31 | Jun 23 | May 16 | Sep 5 | 95 |
| SILVER CITY 5 W | May 31 | Jun 17 | May 4 | Oct 6 | 128 |
| GARDEN VALLEY | Jun 1 | Jun 20 | May 13 | Sep 10 | 102 |
| GIBBONSVILLE #2 | Jun 1 | Jun 19 | May 14 | Sep 17 | 107 |
| MACKAY LOST RVR RS | Jun 1 | Jun 21 | May 13 | Sep 20 | 109 |
| MALTA 4 ESE | Jun 1 | Jun 19 | May 10 | Sep 19 | 111 |
| HAMER 4 NW | Jun 3 | Jun 21 | May 15 | Sep 11 | 98 |
| PIERCE | Jun 3 | Jun 29 | May 17 | Sep 7 | 93 |
| MALTA | Jun 5 | Jun 23 | May 19 | Sep 13 | 96 |
| SMALL 6N | Jun 5 | Jun 21 | May 11 | Sep 20 | 106 |
| LOWMAN | Jun 6 | Jul 1 | May 18 | Sep 4 | 87 |
| FAIRFIELD RS | Jun 8 | Jun 28 | May 15 | Sep 14 | 97 |
| IDAHO FALLS 16 SE | Jun 9 | Jun 26 | May 19 | Sep 11 | 93 |
| MCCALL AP | Jun 10 | Jun 28 | May 21 | Sep 10 | 93 |
| MULLAN PASS VOR/DME | Jun 10 | Jun 25 | May 21 | Sep 23 | 104 |
| IDAHO FALLS 46 W | Jun 11 | Jul 1 | May 20 | Sep 6 | 89 |
| MAY 2SSE | Jun 12 | Jun 29 | May 24 | Sep 6 | 85 |
| MONTEVIEW | Jun 12 | Jun 30 | May 21 | Sep 7 | 87 |
| YELLOWPINE | Jun 12 | Jul 5 | May 21 | Sep 11 | 88 |
| DRIGGS | Jun 13 | Jun 28 | May 27 | Sep 9 | 86 |
| CHILLY BARTON FLAT | Jun 14 | Jun 30 | May 27 | Sep 8 | 86 |
| TETONIA EXP STN | Jun 15 | Jun 29 | May 24 | Sep 7 | 85 |
| HILL CITY 1 W | Jun 16 | Jul 3 | May 31 | Sep 6 | 80 |
| PICABO | Jun 16 | Jun 30 | Jun 3 | Sep 9 | 85 |
| BERN | Jun 17 | Jul 4 | May 31 | Sep 3 | 77 |
| IDAHO CITY | Jun 17 | Jul 4 | May 30 | Sep 5 | 80 |
| CRATERS OF THE MOON | Jun 19 | Jul 2 | Jun 5 | Sep 9 | 81 |
| MCCALL | Jun 22 | Jul 10 | Jun 3 | Sep 2 | 72 |
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.