Data: 2023 USDA zones (PRISM/OSU) · NOAA 1991–2020 normals · updated

Planting zone for Great Falls, MT

Great Falls, MT is in USDA zone 4b across its 5 ZIP codes. The median last spring frost is May 6 and the first fall frost October 1.

Great Falls on the zone map

Outlined: its 3 ZIP code areas · tap the map for the zone at any spot · scroll or pinch to zoom

Not the official USDA Plant Hardiness Zone Map. Zones come from the 2023 USDA hardiness-zone data by the PRISM Group, Oregon State University; we re-mapped and recolored them. The official map is at planthardiness.ars.usda.gov.

Zone4b−25 to −20 °F
ZIP codes5
Last frostMay 6
First frostOct 1
Growing season147 days

4b 5 ZIPs

Frost forecast — next 7 nights

live from the National Weather Service

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Forecast data: National Weather Service (api.weather.gov), public domain. This is not a warning service — for official frost and freeze warnings see weather.gov.

Frost dates in Great Falls, MT

JanFebMarAprMayJunJulAugSepOctNovDec
Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free
Last spring frostMay 6median — 50% chance of a later frost
Safe for tender plantsMay 19only 10% chance of frost after
First fall frostOctober 1median — 10% chance by Sep 17
Growing season147 daysfrost-free, median

A hard freeze (28 °F) usually ends around April 24 and returns around October 11.

From the NOAA station Great Falls 16st, MT, elevation 3,504 ft. NOAA NCEI U.S. Climate Normals 1991–2020, 32 °F threshold. Low spots and valleys can freeze later in spring than the station.

When to plant vegetables in Great Falls

JanFebMarAprMayJunJulAugSepOctNovDec
PeasSow outdoors · Mar 25 – Apr 8
SpinachSow outdoors · Mar 25 – Apr 15
Broccoli, cabbageStart indoors · Feb 25 – Mar 11
Broccoli, cabbageTransplant · Apr 15 – Apr 29
Onion setsPlant outdoors · Apr 8 – Apr 22
PotatoesPlant outdoors · Apr 15 – Apr 29
LettuceSow outdoors · Apr 8 – Apr 22
Carrots, beetsSow outdoors · Apr 15 – Apr 29
TomatoesStart indoors · Mar 11 – Mar 25
TomatoesTransplant · May 13 – May 27
Peppers, eggplantStart indoors · Feb 25 – Mar 11
Peppers, eggplantTransplant · May 20 – Jun 3
BeansSow outdoors · May 13 – May 27
Sweet cornSow outdoors · May 13 – May 27
Cucumbers, squashSow outdoors · May 13 – May 27
Fall lettuce, spinachSow outdoors · Aug 6 – Aug 20
GarlicPlant cloves · Sep 17 – Oct 22
Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (May 6) and first fall frost (Oct 1) with the rules of thumb U.S. extension services publish. Cool-season crops take a light frost; warm-season crops do best once the soil is above about 60 °F.

When spring arrived in 2026

In 2026, spring leaf-out near 59401 came on Mar 5 — 33 days earlier than the 1991–2020 average (Apr 7).

JanFebMarAprMayJun

The Spring Index marks the day when accumulated warmth is enough for lilac and honeysuckle to leaf out — a widely used signal that the growing season has started. Source: USA National Phenology Network, www.usanpn.org — Spring Indices, first leaf, 2026 (data as of 2026-09-08) and 30-year average 1991–2020 (CC BY 4.0).

Native plants for zone 4b in Montana

506 plants native to the lower 48 states, recorded in Montana, and rated by the USDA to survive −25 °F or colder — the bottom of zone 4b. Each links to its USDA PLANTS profile.

Trees 23

American elm120 ft · blooms early spring · medium shade tolerance · to −46 °Fbalsam poplar80 ft · blooms late spring · high shade tolerance · to −79 °Fblack locust60 ft · blooms spring · high shade tolerance · to −37 °Fboxelder60 ft · blooms early spring · low shade tolerance · to −46 °FDouglas-fir200 ft · blooms mid spring · medium shade tolerance · to −33 °Feastern cottonwood190 ft · blooms spring · high shade tolerance · to −43 °F

Shrubs 87

alderleaf buckthorn3 ft · blooms late spring · low shade tolerance · to −33 °Falderleaf mountain mahogany15 ft · blooms late spring · medium shade tolerance · to −41 °Falpine laurel1 ft · blooms late spring · low shade tolerance · to −28 °FAmerican black currant3 ft · blooms early spring · to −46 °FAmerican plum24 ft · blooms mid spring · high shade tolerance · to −38 °Fantelope bitterbrush6 ft · blooms early spring · medium shade tolerance · to −36 °F

Wildflowers & perennials 229

alkali buttercup1 ft · blooms late spring · low shade tolerance · to −38 °Falpine bistort1 ft · blooms mid spring · high shade tolerance · to −38 °Falpine mountainsorrel1 ft · blooms mid summer · medium shade tolerance · to −43 °Falpine sweetvetch2 ft · blooms early summer · high shade tolerance · to −62 °FAmerican alpine speedwell1 ft · blooms summer · medium shade tolerance · to −28 °FAmerican bistort1.5 ft · blooms mid spring · high shade tolerance · to −38 °F

Grasses 155

Alaska oniongrass3 ft · blooms mid spring · low shade tolerance · to −33 °Falkali cordgrass3 ft · blooms late summer · high shade tolerance · to −38 °Falkali sacaton3 ft · blooms mid summer · high shade tolerance · to −38 °FAlpine Meadow-Foxtail0.5 ft · blooms mid spring · medium shade tolerance · to −33 °Falpine timothy1.4 ft · blooms late spring · medium shade tolerance · to −43 °Fanalogue sedge1.5 ft · blooms late spring · medium shade tolerance · to −38 °F

Vines 3

American bittersweet15 ft · blooms spring · low shade tolerance · to −38 °Friverbank grape45 ft · blooms late spring · medium shade tolerance · to −33 °Fwestern white clematis1 ft · blooms mid summer · medium shade tolerance · to −38 °F

Source: USDA, NRCS. 2026. The PLANTS Database (plants.usda.gov), National Plant Data Team — state distribution, native status and the “Temperature, Minimum” characteristic. Check light, moisture and soil needs before buying; local nurseries and your state native plant society can confirm what thrives in Great Falls, MT.

Soil in Great Falls, MT

The soil mapped at the center of ZIP 59401 is Ipano — loam, well drained.

TextureLoama good balance for most vegetables
pH7.9alkaline; most vegetables like 6.0–7.0
DrainageWell drainednatural drainage class
Organic matter2%moderate
Hydrologic groupCwater soaks in slowly
Farmland classFarmland of statewide importanceUSDA classification

Map unit: Ipano-Hillon complex, 0 to 4 percent slopes.

Soil Survey Staff, Natural Resources Conservation Service, USDA. Soil Survey Geographic (SSURGO) Database, via Soil Data Access, accessed 2026-10-29. The soil at the center point of ZIP 59401; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Great Falls, MT

Summer high86 °Faverage high, July
Winter low18 °Faverage low, January
Hot days25days a year at 90 °F or more
Freezing nights143nights a year at 32 °F or less
Growing degree days2,214base 50 °F — the season’s usable heat
Longest day15 h 58 mindaylight on June 21
Shortest day8 h 26 mindaylight on December 21
Onions to growLong-daysummer days reach 15+ hours, enough for long-day varieties (intermediate types work too)
Precipitation15.4 inper year, rain and melted snow

Average high and low, by month

10°20°30°40°50°60°70°80°90°100°32 °FJanuary: average high 37 °F, low 18 °F 37°18° JanFebruary: average high 39 °F, low 19 °F 39°19° FebMarch: average high 48 °F, low 25 °F 48°25° MarApril: average high 58 °F, low 33 °F 58°33° AprMay: average high 67 °F, low 42 °F 67°42° MayJune: average high 75 °F, low 50 °F 75°50° JunJuly: average high 86 °F, low 55 °F 86°55° JulAugust: average high 84 °F, low 53 °F 84°53° AugSeptember: average high 73 °F, low 45 °F 73°45° SepOctober: average high 59 °F, low 36 °F 59°36° OctNovember: average high 45 °F, low 26 °F 45°26° NovDecember: average high 37 °F, low 20 °F 37°20° Dec

Precipitation by month inches

0″1″2″3″January: 0.61 in precipitation 0.6 JanFebruary: 0.58 in precipitation 0.6 FebMarch: 0.63 in precipitation 0.6 MarApril: 1.79 in precipitation 1.8 AprMay: 2.66 in precipitation 2.7 MayJune: 2.74 in precipitation 2.7 JunJuly: 1.34 in precipitation 1.3 JulAugust: 1.30 in precipitation 1.3 AugSeptember: 1.39 in precipitation 1.4 SepOctober: 1.13 in precipitation 1.1 OctNovember: 0.70 in precipitation 0.7 NovDecember: 0.56 in precipitation 0.6 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Great Falls 16st, MT (2 mi away); precipitation: Great Falls 16st, MT (2 mi away). Daylight is calculated from latitude.

ZIP codes in Great Falls

594014b
−25 to −20 °F
594034b
−25 to −20 °F
594044b
−25 to −20 °F
594054b
−25 to −20 °F
594064b
−25 to −20 °F

Montana planting zones →

Questions about Great Falls

What planting zone is Great Falls, MT?

Great Falls, MT is in USDA hardiness zone 4b on the 2023 map (4b: −25 to −20 °F).

When is the last frost in Great Falls, MT?

The median last spring frost is May 6 and the median first fall frost is October 1 (NOAA 1991–2020 normals, Great Falls 16st station).

When can I plant a garden in Great Falls, MT?

Cool-season crops like peas and spinach go in around Mar 25 – Apr 15; tomatoes, peppers, beans and squash after about May 13, once frost risk has passed.

What kind of onions grow in Great Falls, MT?

Long-day onions: the longest day is 15 h 58 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).

How much rain and snow does Great Falls, MT get?

About 15.4 inches of precipitation a year (NOAA 1991–2020 normals).