In Montana, the last spring frost usually comes between May 14 and June 12, and the first fall frost between September 2 and September 26, depending on where you live. Most of Montana is in USDA hardiness zones 3b to 6a. In the highest mountain areas, frost is possible in any month.
Find the frost dates for your ZIP code
Frost dates from NOAA 1991–2020 U.S. Climate Normals, nearest weather station. Zones derived from the 2023 USDA Plant Hardiness Zone Map data (PRISM Climate Group, Oregon State University). This is not the official USDA Plant Hardiness Zone Map.
Frost dates for Montana cities
Dates come from the NOAA weather station closest to each city. The last spring frost and first fall frost are the typical dates, with a 30% chance of frost after (or before) them. The safer planting date has only a 10% chance of a later spring frost: use it for tender plants like tomatoes, peppers and basil.
| City | Zone | Last frost | Safer date | First frost |
|---|---|---|---|---|
| Billings | 5a | May 11 | May 21 | Sep. 28 |
| Missoula | 5b | May 17 | May 28 | Sep. 26 |
| Great Falls | 4b | May 11 | May 19 | Sep. 25 |
| Bozeman | 5a | June 3 | June 14 | Sep. 16 |
| Butte | 5a | June 21 | July 1 | Aug. 31 |
| Helena | 5a | May 15 | May 25 | Sep. 25 |
| Kalispell | 5b | June 7 | June 22 | Sep. 4 |
| Havre | 3b | May 20 | May 27 | Sep. 19 |
| Miles City | 4b | May 13 | May 21 | Sep. 26 |
| Sidney | 4a | May 17 | May 25 | Sep. 22 |
Frost dates vary a lot across Montana. Among the cities above, Billings has the earliest last frost (around May 11) and Butte the latest (around June 21), about 6 weeks apart. Elevation, nearby water and local terrain all make a difference, so use the dates for the place closest to you, or look up your ZIP code.
Growing zones in Montana
Most of Montana is in USDA hardiness zones 3b to 6a. A typical frost-free growing season lasts about 132 days, longer in the warmest areas and shorter in the coldest.
Find planting dates for the main zones in Montana:
- Zone 3 (about 7% of ZIP codes): Tomatoes, Peppers, Potatoes, Lettuce, Green beans, Cucumbers, Garlic, Tulips
- Zone 4 (about 52% of ZIP codes): Tomatoes, Peppers, Potatoes, Lettuce, Green beans, Cucumbers, Garlic, Tulips
- Zone 5 (about 32% of ZIP codes): Tomatoes, Peppers, Potatoes, Lettuce, Green beans, Cucumbers, Garlic, Tulips
- Zone 6 (about 8% of ZIP codes): Tomatoes, Peppers, Potatoes, Lettuce, Green beans, Cucumbers, Garlic, Tulips
See all crops in our planting guides, or build a planting calendar for your ZIP code.
How to use frost dates
- Cool-season crops such as peas, lettuce, spinach and onions can go in several weeks before your last spring frost.
- Warm-season crops such as tomatoes, peppers, squash and beans wait until after it, when the soil has warmed.
- Fall crops are timed back from your first fall frost, and garlic and tulips are planted around it.
- Frost dates are averages. Check the forecast before setting out tender plants.
Frequently asked questions
When is the last frost in Montana?
It depends on where you live. Across most of Montana, the last spring frost comes between May 14 and June 12. In Billings, it is around May 11.
When is the first frost in Montana?
Across most of Montana, the first fall frost comes between September 2 and September 26. In Billings, it is around September 28.
What planting zone is Montana?
Most of Montana is in USDA hardiness zones 3b to 6a. Enter your ZIP code above to find your exact zone.
When can I plant tomatoes in Montana?
Plant tomatoes outside after your last frost, once nights stay above 50 °F. In Billings, the safer date, with only a 10% chance of a later frost, is around May 21. See when to plant tomatoes in zone 5.
Sources. Frost dates come from the nearest NOAA weather station to each city or ZIP code. Zones come from the 2023 USDA Plant Hardiness Zone Map ZIP code data. Our zone lookup is not the official USDA map.