What Planting Zones Are in Montana?
Montana spans USDA hardiness zones 3b to 6b, where the average coldest winter night ranges from −35 °F to 0 °F (−37.2 °C to −17.8 °C). Zone 4b covers the most ZIP codes, 32%, and zones 4a to 5a together cover 78% of the state.
- Zone 3b6% · 25 ZIPs
- Zone 4a18% · 71 ZIPs
- Zone 4b32% · 129 ZIPs
- Zone 5a28% · 111 ZIPs
- Zone 5b8% · 32 ZIPs
- Zone 6a8% · 30 ZIPs
- Zone 6b<1% · 1 ZIP
Bars show each zone's share of the 399 Montana ZIP codes in the official 2023 USDA ZIP code table; select a zone for its temperatures and hardy plants.
What Hardiness Zone Are Montana Cities In?
Billings is in zone 5a, Missoula is in zone 5b, Great Falls is in zone 4b and Bozeman is in zone 5a. The table lists the zone, winter low and average frost dates for 18 Montana cities, using the ZIP code nearest each city center.
| City | ZIP | Zone | Winter low | Last frost | First frost |
|---|---|---|---|---|---|
| Billings | 59102 | 5a | −20 °F to −15 °F | May 5 | Oct 3 |
| Missoula | 59801 | 5b | −15 °F to −10 °F | May 10 | Oct 1 |
| Great Falls | 59401 | 4b | −25 °F to −20 °F | May 6 | Oct 1 |
| Bozeman | 59718 | 5a | −20 °F to −15 °F | May 23 | Sep 23 |
| Butte | 59750 | 5a | −20 °F to −15 °F | Jun 13 | Sep 5 |
| Helena | 59623 | 5a | −20 °F to −15 °F | May 9 | Sep 30 |
| Kalispell | 59901 | 5b | −15 °F to −10 °F | May 31 | Sep 10 |
| Belgrade | 59741 | 5a | −20 °F to −15 °F | May 26 | Sep 15 |
| Anaconda | 59711 | 5a | −20 °F to −15 °F | Jun 1 | Sep 14 |
| Whitefish | 59937 | 5a | −20 °F to −15 °F | May 16 | Sep 25 |
| Havre | 59501 | 3b | −35 °F to −30 °F | May 15 | Sep 23 |
| Livingston | 59047 | 5a | −20 °F to −15 °F | May 19 | Sep 25 |
| Miles City | 59301 | 4b | −25 °F to −20 °F | May 8 | Sep 30 |
| Lewistown | 59457 | 4b | −25 °F to −20 °F | May 14 | Sep 28 |
| Sidney | 59270 | 4a | −30 °F to −25 °F | May 11 | Sep 27 |
| Polson | 59860 | 6a | −10 °F to −5 °F | May 10 | Oct 5 |
| Hamilton | 59840 | 5b | −15 °F to −10 °F | May 21 | Sep 22 |
| Glendive | 59330 | 4a | −30 °F to −25 °F | May 3 | Oct 4 |
Zone: 2023 USDA ZIP code table for the ZIP code nearest each city's Census center point. Frost dates: 50% (median) dates from the nearest NOAA station, 1991–2020 normals. Cities: the largest Montana places by 2024 Census population estimates, spread across the state, plus the largest place in each common zone. Large cities can span two half zones.
Which Parts of Montana Are in Each Zone?
Zone 3b, the coldest Montana zone, covers 6% of ZIP codes around Havre, Plentywood and Chinook. Zone 6a, the warmest with towns, covers 8% around Polson, Libby and Ronan. The table lists the largest places in every zone.
| Zone | Avg. coldest night | Share of ZIPs | Largest places in this zone |
|---|---|---|---|
| Zone 3b | −35 °F to −30 °F | 6% (25) | Havre, Plentywood, Chinook |
| Zone 4a | −30 °F to −25 °F | 18% (71) | Sidney, Glendive, Shelby, Glasgow |
| Zone 4b | −25 °F to −20 °F | 32% (129) | Great Falls, Miles City, Lewistown, Hardin |
| Zone 5a | −20 °F to −15 °F | 28% (111) | Billings, Bozeman, Butte, Helena |
| Zone 5b | −15 °F to −10 °F | 8% (32) | Missoula, Kalispell, Hamilton, Stevensville |
| Zone 6a | −10 °F to −5 °F | 8% (30) | Polson, Libby, Ronan, Thompson Falls |
| Zone 6b | −5 °F to 0 °F | <1% (1) | Rural ZIP codes only |
Places: incorporated places with 1,000+ residents, assigned the zone of the ZIP code nearest their Census center point.
What Do the Hardiness Zones Mean for Montana Gardeners?
A Montana gardener in zone 6b sees winter lows about 30 °F milder than one in zone 3b, so a shrub or perennial that thrives in one part of the state can die in another. Choose plants rated to your own ZIP code's zone or colder.
Hardiness zones follow latitude, elevation and large bodies of water rather than state lines. Higher ground and inland valleys that trap cold air usually sit in colder half zones, while cities, coasts and large lakes moderate winter lows. Within Montana, a plant labelled “zones 4–5” survives winter in at least 78% of ZIP codes, but plants at the edge of their range benefit from mulch and a sheltered spot. Enter a ZIP code in the USDA hardiness zone finder by ZIP code to check your exact half zone before buying perennials.
A zone describes winter cold only. Summer heat, humidity, rainfall and soil decide whether a cold-hardy plant thrives, and planting dates for vegetables follow frost dates, not zones: two Montana towns in the same zone can have last frosts weeks apart.
What Plants Grow Well Across Montana?
154 plants in PlantoScan's catalogue are hardy in every zone from 4a to 5a, the zones that cover 78% of Montana ZIP codes. Popular examples include peony, daisy and poppy.
Peony
Paeonia lactiflora
Zone 3 – 8
AI generated
- DaisyBellis perennisPlantoScan
Daisy
Bellis perennis
Zone 4a – 8b
Poppy
Papaver somniferum
Zone 3a – 9b
AI generated
Daffodil
Narcissus poeticus
Zone 3 – 8
AI generated
Alfalfa
Medicago sativa
Zone 3a – 10a
AI generated
Hyacinth
Hyacinthus orientalis
Zone 4 – 8
AI generated
Tiger Lily
Lilium lancifolium
Zone 3 – 8
AI generated
Forget Me Not
Myosotis sylvatica
Zone 3 – 8
AI generated
Lemon Balm
Melissa officinalis
Zone 4a – 9b
Image: PlantoScan
Hardiness ranges come from PlantoScan's plant database; gardeners in Montana's colder or warmer edge zones should check each plant's full range.
When Is the Last Frost in Montana?
Across most Montana ZIP codes, the average last spring frost falls between May 9 and June 6, from May 3 in Glendive to June 13 in Butte. Tender vegetables such as tomatoes go out 1 to 2 weeks after the local date.
The last and first frost dates for Montana cities include the safer 90% planting date, the fall frost date, growing season length and a tomato planting table for each city.
Frequently Asked Questions
- What planting zone is Montana?
- Montana spans USDA hardiness zones 3b to 6b on the 2023 USDA Plant Hardiness Zone Map. Zone 4b is the most common, covering 32% of the state's 399 ZIP codes, and zones 4a to 5a together cover 78%.
- What hardiness zone is Billings, Montana?
- Billings is in USDA hardiness zone 5a (ZIP 59102), where the average coldest winter night reaches −20 °F to −15 °F. Its average last spring frost is May 5 and its first fall frost October 3.
- What hardiness zone is Missoula, Montana?
- Missoula is in USDA hardiness zone 5b (ZIP 59801), where the average coldest winter night reaches −15 °F to −10 °F. Its average last spring frost is May 10 and its first fall frost October 1.
- What hardiness zone is Great Falls, Montana?
- Great Falls is in USDA hardiness zone 4b (ZIP 59401), where the average coldest winter night reaches −25 °F to −20 °F. Its average last spring frost is May 6 and its first fall frost October 1.
- What is the coldest hardiness zone in Montana?
- Zone 3b (−35 °F to −30 °F) is the coldest zone in Montana, found in 25 ZIP codes around Havre and Plentywood. The warmest is zone 6b (−5 °F to 0 °F).
Zones: 2023 USDA Plant Hardiness Zone Map ZIP code table, USDA Agricultural Research Service and the PRISM Climate Group, Oregon State University, used without changes. Frost dates: NOAA National Centers for Environmental Information, 1991–2020 U.S. Climate Normals. City locations and populations: U.S. Census Bureau Gazetteer files and Vintage 2024 population estimates. PlantoScan is not affiliated with or endorsed by these agencies.