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

Planting zone for 59921 — Lake Mc Donald, MT

ZIP code 59921 (Lake Mc Donald, Flathead County) is in USDA zone 5a: the coldest winter night averages −20 to −15 °F. The median last spring frost is May 9 and the first fall frost October 1.

Where ZIP 59921 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.

Zone5a−20 to −15 °F
Coldest night−28.9 to −26.1 °C
Last frostMay 9
First frostOct 1
2012 zone5a

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 5a means →

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for Lake Mc Donald, 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 Lake Mc Donald, MT

JanFebMarAprMayJunJulAugSepOctNovDec
Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free
Last spring frostMay 9median — 50% chance of a later frost
Safe for tender plantsMay 30only 10% chance of frost after
First fall frostOctober 1median — 10% chance by Sep 13
Growing season141 daysfrost-free, median

A hard freeze (28 °F) usually ends around April 27 and returns around October 14.

From the NOAA station Hungry Horse Dam, MT — 4 miles away, elevation 3,160 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 59921

JanFebMarAprMayJunJulAugSepOctNovDec
PeasSow outdoors · Mar 28 – Apr 11
SpinachSow outdoors · Mar 28 – Apr 18
Broccoli, cabbageStart indoors · Feb 28 – Mar 14
Broccoli, cabbageTransplant · Apr 18 – May 2
Onion setsPlant outdoors · Apr 11 – Apr 25
PotatoesPlant outdoors · Apr 18 – May 2
LettuceSow outdoors · Apr 11 – Apr 25
Carrots, beetsSow outdoors · Apr 18 – May 2
TomatoesStart indoors · Mar 14 – Mar 28
TomatoesTransplant · May 16 – May 30
Peppers, eggplantStart indoors · Feb 28 – Mar 14
Peppers, eggplantTransplant · May 23 – Jun 6
BeansSow outdoors · May 16 – May 30
Sweet cornSow outdoors · May 16 – May 30
Cucumbers, squashSow outdoors · May 16 – May 30
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 9) 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 59921 came on Apr 27 — 4 days earlier than the 1991–2020 average (May 1).

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 5a in Montana

548 plants native to the lower 48 states, recorded in Montana, and rated by the USDA to survive −20 °F or colder — the bottom of zone 5a. Each links to its USDA PLANTS profile.

Trees 26

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 96

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 253

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 161

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 Lake Mc Donald, MT.

Soil in Lake Mc Donald, MT

The center of ZIP 59921 is mapped as Water: built-over ground without natural soil data. Garden soil here is usually imported or disturbed — test before you plant.

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 59921; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Lake Mc Donald, MT

Summer high82 °Faverage high, July
Winter low20 °Faverage low, January
Hot days16days a year at 90 °F or more
Freezing nights169nights a year at 32 °F or less
Growing degree days1,735base 50 °F — the season’s usable heat
Longest day16 h 06 mindaylight on June 21
Shortest day8 h 19 mindaylight on December 21
Onions to growLong-daysummer days reach 15+ hours, enough for long-day varieties (intermediate types work too)
Precipitation34.6 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 31 °F, low 20 °F 31°20° JanFebruary: average high 34 °F, low 20 °F 34°20° FebMarch: average high 43 °F, low 25 °F 43°25° MarApril: average high 53 °F, low 32 °F 53°32° AprMay: average high 64 °F, low 41 °F 64°41° MayJune: average high 71 °F, low 47 °F 71°47° JunJuly: average high 82 °F, low 53 °F 82°53° JulAugust: average high 81 °F, low 52 °F 81°52° AugSeptember: average high 69 °F, low 44 °F 69°44° SepOctober: average high 52 °F, low 35 °F 52°35° OctNovember: average high 38 °F, low 28 °F 38°28° NovDecember: average high 31 °F, low 21 °F 31°21° Dec

Precipitation by month inches

0″1″2″3″4″January: 3.62 in precipitation 3.6 JanFebruary: 2.53 in precipitation 2.5 FebMarch: 3.21 in precipitation 3.2 MarApril: 2.65 in precipitation 2.6 AprMay: 2.87 in precipitation 2.9 MayJune: 3.82 in precipitation 3.8 JunJuly: 1.42 in precipitation 1.4 JulAugust: 1.23 in precipitation 1.2 AugSeptember: 2.21 in precipitation 2.2 SepOctober: 3.52 in precipitation 3.5 OctNovember: 3.88 in precipitation 3.9 NovDecember: 3.66 in precipitation 3.7 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Hungry Horse Dam, MT (4 mi away); precipitation: Hungry Horse Dam, MT (4 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

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

599265b
Martin City, MT · 4 mi
599195b
Hungry Horse, MT · 7 mi
599135a
Coram, MT · 9 mi
599165a
Essex, MT · 13 mi
599125a
Columbia Falls, MT · 14 mi
599045b
Kalispell, MT · 15 mi
599015b
Kalispell, MT · 21 mi
599326a
Somers, MT · 22 mi

Montana planting zones →

Questions about 59921

What planting zone is ZIP code 59921?

ZIP code 59921 (Lake Mc Donald, MT) is in USDA hardiness zone 5a on the 2023 map: the coldest night of an average winter reaches −20 to −15 °F (−28.9 to −26.1 °C).

When is the last frost in Lake Mc Donald, MT?

The median last spring frost (32 °F) near 59921 is May 9; after May 30 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Hungry Horse Dam station.

When is the first frost in Lake Mc Donald, MT?

The median first fall frost near 59921 is October 1, giving a median frost-free growing season of 141 days.

When should I plant tomatoes in 59921?

Start tomato seeds indoors around Mar 14 – Mar 28 and set transplants outside around May 16 – May 30, one to three weeks after the median last frost.

How much rain and snow does 59921 get?

About 34.6 inches of precipitation a year (NOAA 1991–2020 normals, Hungry Horse Dam station).

How hot do summers get in Lake Mc Donald, MT?

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

Did spring come early in Lake Mc Donald, MT in 2026?

Spring leaf-out near 59921 came on Apr 27 in 2026, 4 days earlier than the 1991–2020 average (May 1), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Lake Mc Donald, MT?

Long-day onions: the longest day near 59921 is 16 h 06 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).