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

Planting zone for 59870 — Stevensville, MT

ZIP code 59870 (Stevensville, Ravalli County) is in USDA zone 5b: the coldest winter night averages −15 to −10 °F. The median last spring frost is May 22 and the first fall frost September 19.

Where ZIP 59870 is

Outlined: the ZIP code area · 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.

Zone5b−15 to −10 °F
Coldest night−26.1 to −23.3 °C
Last frostMay 22
First frostSep 19
2012 zone5a

Was 5a on the 2012 map — half a zone warmer now. The zone is the one at the center of the ZIP code; hilly ZIPs can span two zones. What zone 5b means →

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for Stevensville, MT…

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 Stevensville, MT

JanFebMarAprMayJunJulAugSepOctNovDec
Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free
Last spring frostMay 22median — 50% chance of a later frost
Safe for tender plantsJune 13only 10% chance of frost after
First fall frostSeptember 19median — 10% chance by Sep 3
Growing season115 daysfrost-free, median

A hard freeze (28 °F) usually ends around May 5 and returns around October 1.

From the NOAA station Stevensville, MT — within 1 mile, elevation 3,376 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 59870

JanFebMarAprMayJunJulAugSepOctNovDec
PeasSow outdoors · Apr 10 – Apr 24
SpinachSow outdoors · Apr 10 – May 1
Broccoli, cabbageStart indoors · Mar 13 – Mar 27
Broccoli, cabbageTransplant · May 1 – May 15
Onion setsPlant outdoors · Apr 24 – May 8
PotatoesPlant outdoors · May 1 – May 15
LettuceSow outdoors · Apr 24 – May 8
Carrots, beetsSow outdoors · May 1 – May 15
TomatoesStart indoors · Mar 27 – Apr 10
TomatoesTransplant · May 29 – Jun 12
Peppers, eggplantStart indoors · Mar 13 – Mar 27
Peppers, eggplantTransplant · Jun 5 – Jun 19
BeansSow outdoors · May 29 – Jun 12
Sweet cornSow outdoors · May 29 – Jun 12
Cucumbers, squashSow outdoors · May 29 – Jun 12
Fall lettuce, spinachSow outdoors · Jul 25 – Aug 8
GarlicPlant cloves · Sep 5 – Oct 10
Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (May 22) and first fall frost (Sep 19) 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 59870 came on Mar 27 — 12 days earlier than the 1991–2020 average (Apr 8).

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 5b in Montana

561 plants native to the lower 48 states, recorded in Montana, and rated by the USDA to survive −15 °F or colder — the bottom of zone 5b. Each links to its USDA PLANTS profile.

Trees 28

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 97

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 259

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 164

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 Stevensville, MT.

Soil in Stevensville, MT

The soil mapped at the center of ZIP 59870 is Grayhorse — silt loam, somewhat poorly drained.

TextureSilt loama good balance for most vegetables
pH8.0alkaline; most vegetables like 6.0–7.0
DrainageSomewhat poorly drainedconsider raised beds
Organic matter5%high
Hydrologic groupCwater soaks in slowly
Farmland classFarmland of local importanceUSDA classification

Map unit: Grayhorse-Owenfort complex, 0 to 2 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 59870; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Stevensville, MT

Summer high85 °Faverage high, July
Winter low19 °Faverage low, January
Hot days28days a year at 90 °F or more
Freezing nights175nights a year at 32 °F or less
Growing degree days1,760base 50 °F — the season’s usable heat
Longest day15 h 50 mindaylight on June 21
Shortest day8 h 34 mindaylight on December 21
Onions to growLong-daysummer days reach 15+ hours, enough for long-day varieties (intermediate types work too)
Precipitation12.4 inper year, rain and melted snow
Snowfall17 inper year; 24 days with snow on the ground

Average high and low, by month

10°20°30°40°50°60°70°80°90°100°32 °FJanuary: average high 35 °F, low 19 °F 35°19° JanFebruary: average high 38 °F, low 21 °F 38°21° FebMarch: average high 50 °F, low 26 °F 50°26° MarApril: average high 58 °F, low 32 °F 58°32° AprMay: average high 68 °F, low 39 °F 68°39° MayJune: average high 75 °F, low 45 °F 75°45° JunJuly: average high 85 °F, low 49 °F 85°49° JulAugust: average high 84 °F, low 47 °F 84°47° AugSeptember: average high 74 °F, low 40 °F 74°40° SepOctober: average high 58 °F, low 32 °F 58°32° OctNovember: average high 43 °F, low 25 °F 43°25° NovDecember: average high 33 °F, low 19 °F 33°19° Dec

Precipitation by month inches · ❄ = snowfall

0″1″2″January: 1.00 in precipitation, 4 in snowfall 1.0❄4 JanFebruary: 0.92 in precipitation, 3 in snowfall 0.9❄3 FebMarch: 0.77 in precipitation, 1.5 in snowfall 0.8❄2 MarApril: 0.93 in precipitation, 0.1 in snowfall 0.9 AprMay: 1.45 in precipitation 1.4 MayJune: 1.59 in precipitation 1.6 JunJuly: 0.83 in precipitation 0.8 JulAugust: 0.81 in precipitation 0.8 AugSeptember: 0.84 in precipitation 0.8 SepOctober: 1.04 in precipitation, 0.1 in snowfall 1.0 OctNovember: 1.15 in precipitation, 1.6 in snowfall 1.1❄2 NovDecember: 1.12 in precipitation, 6.8 in snowfall 1.1❄7 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Stevensville, MT (within 1 mile); precipitation: Stevensville, MT (within 1 mile). Daylight is calculated from latitude.

Nearby ZIP codes

All 8 nearest ZIP codes share zone 5b.

598335b
Florence, MT · 9 mi
598755b
Victor, MT · 14 mi
598285b
Corvallis, MT · 14 mi
598415b
Pinesdale, MT · 15 mi
598035b
Missoula, MT · 19 mi
598475b
Lolo, MT · 20 mi
598015b
Missoula, MT · 24 mi
598125b
Missoula, MT · 24 mi

Montana planting zones →

Questions about 59870

What planting zone is ZIP code 59870?

ZIP code 59870 (Stevensville, MT) is in USDA hardiness zone 5b on the 2023 map: the coldest night of an average winter reaches −15 to −10 °F (−26.1 to −23.3 °C).

When is the last frost in Stevensville, MT?

The median last spring frost (32 °F) near 59870 is May 22; after June 13 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Stevensville station.

When is the first frost in Stevensville, MT?

The median first fall frost near 59870 is September 19, giving a median frost-free growing season of 115 days.

When should I plant tomatoes in 59870?

Start tomato seeds indoors around Mar 27 – Apr 10 and set transplants outside around May 29 – Jun 12, one to three weeks after the median last frost.

How much rain and snow does 59870 get?

About 12.4 inches of precipitation a year and 17 inches of snowfall (NOAA 1991–2020 normals, Stevensville station).

How hot do summers get in Stevensville, MT?

The average high peaks at 85 °F in July, with about 28 days a year at 90 °F or more.

What kind of soil does 59870 have?

The USDA soil survey maps Grayhorse at the center of ZIP 59870: silt loam, somewhat poorly drained, pH about 8.0 (alkaline).

Did spring come early in Stevensville, MT in 2026?

Spring leaf-out near 59870 came on Mar 27 in 2026, 12 days earlier than the 1991–2020 average (Apr 8), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Stevensville, MT?

Long-day onions: the longest day near 59870 is 15 h 50 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).

Did the zone for 59870 change?

Yes. The 2012 USDA map put 59870 in zone 5a; the 2023 map puts it in zone 5b. The newer map uses 1991–2020 data and more weather stations.