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

Planting zone for 59835 — Grantsdale, MT

ZIP code 59835 (Grantsdale, Ravalli County) is in USDA zone 5b: the coldest winter night averages −15 to −10 °F. The median last spring frost is May 21 and the first fall frost September 22.

Where ZIP 59835 is

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 21
First frostSep 22
2012 zone5b

Same zone as on the 2012 map. 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 Grantsdale, 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 Grantsdale, MT

JanFebMarAprMayJunJulAugSepOctNovDec
Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free
Last spring frostMay 21median — 50% chance of a later frost
Safe for tender plantsJune 6only 10% chance of frost after
First fall frostSeptember 22median — 10% chance by Sep 6
Growing season122 daysfrost-free, median

A hard freeze (28 °F) usually ends around May 5 and returns around October 2.

From the NOAA station Hamilton, MT — 3 miles away, elevation 3,586 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 59835

JanFebMarAprMayJunJulAugSepOctNovDec
PeasSow outdoors · Apr 9 – Apr 23
SpinachSow outdoors · Apr 9 – Apr 30
Broccoli, cabbageStart indoors · Mar 12 – Mar 26
Broccoli, cabbageTransplant · Apr 30 – May 14
Onion setsPlant outdoors · Apr 23 – May 7
PotatoesPlant outdoors · Apr 30 – May 14
LettuceSow outdoors · Apr 23 – May 7
Carrots, beetsSow outdoors · Apr 30 – May 14
TomatoesStart indoors · Mar 26 – Apr 9
TomatoesTransplant · May 28 – Jun 11
Peppers, eggplantStart indoors · Mar 12 – Mar 26
Peppers, eggplantTransplant · Jun 4 – Jun 18
BeansSow outdoors · May 28 – Jun 11
Sweet cornSow outdoors · May 28 – Jun 11
Cucumbers, squashSow outdoors · May 28 – Jun 11
Fall lettuce, spinachSow outdoors · Jul 28 – Aug 11
GarlicPlant cloves · Sep 8 – Oct 13
Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (May 21) and first fall frost (Sep 22) 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 59835 came on Mar 21 — 20 days earlier than the 1991–2020 average (Apr 10).

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 Grantsdale, MT.

Soil in Grantsdale, MT

The soil mapped at the center of ZIP 59835 is Holloron — cobbly loam, well drained.

TextureCobbly loama good balance for most vegetables
pH6.9neutral; most vegetables like 6.0–7.0
DrainageWell drainednatural drainage class
Organic matter3%moderate
Hydrologic groupBwater soaks in moderately
Farmland classFarmland of local importanceUSDA classification

Map unit: Holloron-Tiechute 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 59835; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Grantsdale, MT

Summer high84 °Faverage high, July
Winter low18 °Faverage low, December
Hot days22days a year at 90 °F or more
Freezing nights173nights a year at 32 °F or less
Growing degree days1,654base 50 °F — the season’s usable heat
Longest day15 h 47 mindaylight on June 21
Shortest day8 h 37 mindaylight on December 21
Onions to growLong-daysummer days reach 15+ hours, enough for long-day varieties (intermediate types work too)
Precipitation13.6 inper year, rain and melted snow

Average high and low, by month

10°20°30°40°50°60°70°80°90°32 °FJanuary: average high 35 °F, low 19 °F 35°19° JanFebruary: average high 39 °F, low 20 °F 39°20° FebMarch: average high 49 °F, low 25 °F 49°25° MarApril: average high 56 °F, low 31 °F 56°31° AprMay: average high 66 °F, low 38 °F 66°38° MayJune: average high 73 °F, low 45 °F 73°45° JunJuly: average high 84 °F, low 50 °F 84°50° JulAugust: average high 82 °F, low 48 °F 82°48° AugSeptember: average high 72 °F, low 40 °F 72°40° SepOctober: average high 57 °F, low 31 °F 57°31° OctNovember: average high 43 °F, low 23 °F 43°23° NovDecember: average high 34 °F, low 18 °F 34°18° Dec

Precipitation by month inches

0″1″2″January: 0.96 in precipitation 1.0 JanFebruary: 1.18 in precipitation 1.2 FebMarch: 0.98 in precipitation 1.0 MarApril: 1.12 in precipitation 1.1 AprMay: 1.53 in precipitation 1.5 MayJune: 1.65 in precipitation 1.6 JunJuly: 0.85 in precipitation 0.8 JulAugust: 0.80 in precipitation 0.8 AugSeptember: 0.81 in precipitation 0.8 SepOctober: 0.94 in precipitation 0.9 OctNovember: 1.45 in precipitation 1.4 NovDecember: 1.33 in precipitation 1.3 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Hamilton, MT (3 mi away); precipitation: Hamilton, MT (3 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

1 of the 8 nearest ZIP codes are in a different zone — elevation and distance from water change winter lows quickly.

598405b
Hamilton, MT · 3 mi
598415b
Pinesdale, MT · 10 mi
598285b
Corvallis, MT · 12 mi
598755b
Victor, MT · 17 mi
598275b
Conner, MT · 22 mi
598705b
Stevensville, MT · 22 mi
598715a
Sula, MT · 27 mi
598335b
Florence, MT · 31 mi

Montana planting zones →

Questions about 59835

What planting zone is ZIP code 59835?

ZIP code 59835 (Grantsdale, 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 Grantsdale, MT?

The median last spring frost (32 °F) near 59835 is May 21; after June 6 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Hamilton station.

When is the first frost in Grantsdale, MT?

The median first fall frost near 59835 is September 22, giving a median frost-free growing season of 122 days.

When should I plant tomatoes in 59835?

Start tomato seeds indoors around Mar 26 – Apr 9 and set transplants outside around May 28 – Jun 11, one to three weeks after the median last frost.

How much rain and snow does 59835 get?

About 13.6 inches of precipitation a year (NOAA 1991–2020 normals, Hamilton station).

How hot do summers get in Grantsdale, MT?

The average high peaks at 84 °F in July, with about 22 days a year at 90 °F or more.

What kind of soil does 59835 have?

The USDA soil survey maps Holloron at the center of ZIP 59835: cobbly loam, well drained, pH about 6.9 (neutral).

Did spring come early in Grantsdale, MT in 2026?

Spring leaf-out near 59835 came on Mar 21 in 2026, 20 days earlier than the 1991–2020 average (Apr 10), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Grantsdale, MT?

Long-day onions: the longest day near 59835 is 15 h 47 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).