Frost dates / By state
Frost dates in Montana
NOAA 1991–2020 normals for a 32 °F freeze. Your own yard can run a little either side.
Short answer
Across 22 NOAA weather stations in Montana, the average last spring frost runs from May 4 at Billings Logan Intl Airport to June 15 at Lewistown 42 WSW. The first fall frost comes as early as September 4 at Lewistown 42 WSW and as late as October 7 at Billings Logan Intl Airport. At 2 of the 24 stations, a freeze can come in any month. Planting zones near these stations run from 4a to 6a.
Find yours by ZIP code
The table below is by weather station. For the station nearest you, and your planting zone, type your ZIP code.
Montana frost dates by weather station
| Station | Last spring frost | First fall frost | Frost-free | Zone nearby |
|---|---|---|---|---|
| Baker Muni Airport 2,971 ft | May 16 1 in 10 after May 29 | September 26 1 in 10 by September 11 | 133 days | 4b |
| Billings Logan Intl Airport 3,581 ft | May 4 1 in 10 after May 18 | October 7 1 in 10 by September 26 | 156 days | 5a |
| Bozeman Gallatin Fld 4,427 ft | May 26 1 in 10 after June 12 | September 16 1 in 10 by September 2 | 113 days | – |
| Butte Bert Mooney Airport 5,506 ft | June 13 1 in 10 after July 1 | September 5 1 in 10 by August 24 | 84 days | 5a |
| Cut Bank Muni Airport 3,838 ft | May 24 1 in 10 after June 5 | September 15 1 in 10 by September 1 | 114 days | – |
| Dillon 18 WSW 5,971 ft | A freeze is possible in any month | – | ||
| Dillon Airport 5,200 ft | June 2 1 in 10 after June 21 | September 13 1 in 10 by August 30 | 103 days | – |
| Drummond Aviation 4,000 ft | A freeze is possible in any month | 5b | ||
| Glasgow Intl Airport 2,285 ft | May 6 1 in 10 after May 18 | September 30 1 in 10 by September 17 | 147 days | 4a |
| Great Falls Intl Airport 3,664 ft | May 19 1 in 10 after June 2 | September 24 1 in 10 by September 9 | 128 days | 4b |
| Havre City Co Airport 2,585 ft | May 15 1 in 10 after May 27 | September 23 1 in 10 by September 11 | 131 days | – |
| Helena Rgnl Airport 3,828 ft | May 9 1 in 10 after May 25 | September 30 1 in 10 by September 17 | 144 days | 5a |
| Jordan Airport 2,662 ft | May 18 1 in 10 after May 31 | September 20 1 in 10 by September 8 | 125 days | 4a |
| Lewistown 42 WSW 5,070 ft | June 15 1 in 10 after July 8 | September 4 1 in 10 by August 19 | 81 days | – |
| Lewistown Muni Airport 4,145 ft | May 23 1 in 10 after June 8 | September 21 1 in 10 by September 8 | 121 days | 4b |
| Livingston Mission Fld 4,643 ft | May 27 1 in 10 after June 14 | September 14 1 in 10 by August 27 | 110 days | 5a |
| Miles City F Wiley Fld 2,624 ft | May 8 1 in 10 after May 21 | September 30 1 in 10 by September 17 | 145 days | 4b |
| Missoula Intl Airport 3,192 ft | May 16 1 in 10 after June 1 | September 26 1 in 10 by September 12 | 133 days | 5b |
| St Marie 2,756 ft | May 13 1 in 10 after May 26 | September 27 1 in 10 by September 13 | 137 days | 4a |
| St. Mary 1 SSW 4,555 ft | June 3 1 in 10 after June 23 | September 8 1 in 10 by August 22 | 97 days | 4b |
| Superior 2,710 ft | May 17 1 in 10 after June 8 | September 23 1 in 10 by September 6 | 129 days | 6a |
| Wolf Point 29 ENE 2,085 ft | May 24 1 in 10 after June 6 | September 14 1 in 10 by September 1 | 113 days | 4a |
| Wolf Point 34 NE 2,643 ft | May 13 1 in 10 after May 25 | September 28 1 in 10 by September 14 | 138 days | – |
| Wolf Point Intl Airport 1,986 ft | May 16 1 in 10 after May 29 | September 20 1 in 10 by September 7 | 127 days | 4a |
The average date is NOAA's 50% date: half of years have a later last frost, or an earlier first one. Plan by the 1-in-10 date if a freeze would cost you plants. Stations are NOAA's main weather stations, mostly airports. “Zone nearby” is the USDA 2023 zone of the nearest ZIP code within 10 miles. NOAA counts the frost season from August to July, so in the warmest places the “first fall” freeze lands after New Year.
How these dates work
Frost dates come from NOAA's 1991 to 2020 Climate Normals, which work out from each weather station's daily lows how likely the last spring freeze and the first fall freeze (32 °F) are by each date. We use the station nearest the middle of your ZIP code and show its height and distance, since a station on a hill or by a lake can differ from your yard.
The average date is the 50% date: half of years have a freeze after the spring date or before the fall one. The 1-in-10 dates are NOAA's 10% dates, the ones to plan by if a late freeze would cost you plants. Within one yard, cold air pools in low spots while walls and paving hold heat, so some corners freeze before others.
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Where the numbers come from
- USDA Plant Hardiness Zone Map, 2023. Agricultural Research Service, U.S. Department of Agriculture
- PRISM Climate Group, Oregon State University (zone data)
- NOAA NCEI, U.S. Climate Normals 1991–2020, annual/seasonal
- NOAA, Normals calculation methodology (frost-freeze probability dates)
- US Census Bureau, 2025 ZCTA gazetteer (ZIP code centers)