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

Planting zone for 59911 — Bigfork, MT

ZIP code 59911 (Bigfork, Flathead County) is in USDA zone 5b: the coldest winter night averages −15 to −10 °F. The median last spring frost is May 17 and the first fall frost September 19.

Where ZIP 59911 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 17
First frostSep 19
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 Bigfork, 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 Bigfork, MT

JanFebMarAprMayJunJulAugSepOctNovDec
Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free
Last spring frostMay 17median — 50% chance of a later frost
Safe for tender plantsJune 4only 10% chance of frost after
First fall frostSeptember 19median — 10% chance by Sep 4
Growing season121 daysfrost-free, median

A hard freeze (28 °F) usually ends around April 30 and returns around October 1.

From the NOAA station Swan Lake, MT — 4 miles away, elevation 3,101 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 59911

JanFebMarAprMayJunJulAugSepOctNovDec
PeasSow outdoors · Apr 5 – Apr 19
SpinachSow outdoors · Apr 5 – Apr 26
Broccoli, cabbageStart indoors · Mar 8 – Mar 22
Broccoli, cabbageTransplant · Apr 26 – May 10
Onion setsPlant outdoors · Apr 19 – May 3
PotatoesPlant outdoors · Apr 26 – May 10
LettuceSow outdoors · Apr 19 – May 3
Carrots, beetsSow outdoors · Apr 26 – May 10
TomatoesStart indoors · Mar 22 – Apr 5
TomatoesTransplant · May 24 – Jun 7
Peppers, eggplantStart indoors · Mar 8 – Mar 22
Peppers, eggplantTransplant · May 31 – Jun 14
BeansSow outdoors · May 24 – Jun 7
Sweet cornSow outdoors · May 24 – Jun 7
Cucumbers, squashSow outdoors · May 24 – Jun 7
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 17) 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 59911 came on Apr 6 — 14 days earlier than the 1991–2020 average (Apr 20).

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 Bigfork, MT.

Soil in Bigfork, MT

The soil mapped at the center of ZIP 59911 is Andeptic Cryoboralfs — silt loam.

TextureSilt loama good balance for most vegetables
pH5.4strongly acidic; most vegetables like 6.0–7.0
Organic matter2%moderate
Hydrologic groupCwater soaks in slowly
Farmland classNot prime farmlandUSDA classification

Map unit: Andeptic Cryoboralfs, silty till substratum, calcareous, hilly.

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 59911; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Bigfork, MT

Summer high82 °Faverage high, July
Winter low18 °Faverage low, January
Hot days16days a year at 90 °F or more
Freezing nights204nights a year at 32 °F or less
Growing degree days1,429base 50 °F — the season’s usable heat
Longest day16 h 02 mindaylight on June 21
Shortest day8 h 23 mindaylight on December 21
Onions to growLong-daysummer days reach 15+ hours, enough for long-day varieties (intermediate types work too)
Precipitation21.4 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 31 °F, low 18 °F 31°18° JanFebruary: average high 36 °F, low 18 °F 36°18° FebMarch: average high 45 °F, low 26 °F 45°26° MarApril: average high 54 °F, low 31 °F 54°31° AprMay: average high 64 °F, low 38 °F 64°38° MayJune: average high 71 °F, low 44 °F 71°44° JunJuly: average high 82 °F, low 48 °F 82°48° JulAugust: average high 82 °F, low 46 °F 82°46° AugSeptember: average high 70 °F, low 39 °F 70°39° SepOctober: average high 55 °F, low 32 °F 55°32° OctNovember: average high 39 °F, low 26 °F 39°26° NovDecember: average high 30 °F, low 20 °F 30°20° Dec

Precipitation by month inches

0″1″2″3″4″January: 1.72 in precipitation 1.7 JanFebruary: 1.03 in precipitation 1.0 FebMarch: 1.33 in precipitation 1.3 MarApril: 1.76 in precipitation 1.8 AprMay: 2.52 in precipitation 2.5 MayJune: 3.18 in precipitation 3.2 JunJuly: 1.34 in precipitation 1.3 JulAugust: 1.11 in precipitation 1.1 AugSeptember: 1.73 in precipitation 1.7 SepOctober: 2.41 in precipitation 2.4 OctNovember: 1.73 in precipitation 1.7 NovDecember: 1.56 in precipitation 1.6 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Swan Lake, MT (4 mi away); precipitation: Bigfork 13 S, MT (7 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

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

599106a
Big Arm, MT · 17 mi
598606a
Polson, MT · 17 mi
599316a
Rollins, MT · 18 mi
599226a
Lakeside, MT · 18 mi
599146a
Dayton, MT · 19 mi
599326a
Somers, MT · 21 mi
598556a
Pablo, MT · 21 mi
599296a
Proctor, MT · 24 mi

Montana planting zones →

Questions about 59911

What planting zone is ZIP code 59911?

ZIP code 59911 (Bigfork, 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 Bigfork, MT?

The median last spring frost (32 °F) near 59911 is May 17; after June 4 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Swan Lake station.

When is the first frost in Bigfork, MT?

The median first fall frost near 59911 is September 19, giving a median frost-free growing season of 121 days.

When should I plant tomatoes in 59911?

Start tomato seeds indoors around Mar 22 – Apr 5 and set transplants outside around May 24 – Jun 7, one to three weeks after the median last frost.

How much rain and snow does 59911 get?

About 21.4 inches of precipitation a year (NOAA 1991–2020 normals, Bigfork 13 S station).

How hot do summers get in Bigfork, MT?

The average high peaks at 82 °F in July, with about 16 days a year at 90 °F or more.

What kind of soil does 59911 have?

The USDA soil survey maps Andeptic Cryoboralfs at the center of ZIP 59911: silt loam, pH about 5.4 (strongly acidic).

Did spring come early in Bigfork, MT in 2026?

Spring leaf-out near 59911 came on Apr 6 in 2026, 14 days earlier than the 1991–2020 average (Apr 20), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Bigfork, MT?

Long-day onions: the longest day near 59911 is 16 h 02 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).