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

Planting zone for 59821 — Arlee, MT

ZIP code 59821 (Arlee, Lake County) is in USDA zone 5b: the coldest winter night averages −15 to −10 °F. The median last spring frost is May 12 and the first fall frost October 2.

Where ZIP 59821 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 12
First frostOct 2
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 Arlee, 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 Arlee, MT

JanFebMarAprMayJunJulAugSepOctNovDec
Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free
Last spring frostMay 12median — 50% chance of a later frost
Safe for tender plantsJune 1only 10% chance of frost after
First fall frostOctober 2median — 10% chance by Sep 19
Growing season142 daysfrost-free, median

A hard freeze (28 °F) usually ends around April 30 and returns around October 12.

From the NOAA station Saint Ignatius, MT — 8 miles away, elevation 2,917 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 59821

JanFebMarAprMayJunJulAugSepOctNovDec
PeasSow outdoors · Mar 31 – Apr 14
SpinachSow outdoors · Mar 31 – Apr 21
Broccoli, cabbageStart indoors · Mar 3 – Mar 17
Broccoli, cabbageTransplant · Apr 21 – May 5
Onion setsPlant outdoors · Apr 14 – Apr 28
PotatoesPlant outdoors · Apr 21 – May 5
LettuceSow outdoors · Apr 14 – Apr 28
Carrots, beetsSow outdoors · Apr 21 – May 5
TomatoesStart indoors · Mar 17 – Mar 31
TomatoesTransplant · May 19 – Jun 2
Peppers, eggplantStart indoors · Mar 3 – Mar 17
Peppers, eggplantTransplant · May 26 – Jun 9
BeansSow outdoors · May 19 – Jun 2
Sweet cornSow outdoors · May 19 – Jun 2
Cucumbers, squashSow outdoors · May 19 – Jun 2
Fall lettuce, spinachSow outdoors · Aug 7 – Aug 21
GarlicPlant cloves · Sep 18 – Oct 23
Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (May 12) and first fall frost (Oct 2) 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 59821 came on Apr 27 — 3 days earlier than the 1991–2020 average (Apr 30).

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 Arlee, MT.

Soil in Arlee, MT

The soil mapped at the center of ZIP 59821 is Repp — mucky peat, well drained.

TextureMucky peattop layer
pH6.5neutral; most vegetables like 6.0–7.0
DrainageWell drainednatural drainage class
Organic matter75%high
Hydrologic groupBwater soaks in moderately
Farmland classNot prime farmlandUSDA classification

Map unit: Repp, cool-Rock outcrop complex, 30 to 60 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 59821; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Arlee, MT

Summer high86 °Faverage high, July
Winter low22 °Faverage low, February
Hot days20days a year at 90 °F or more
Freezing nights152nights a year at 32 °F or less
Growing degree days2,070base 50 °F — the season’s usable heat
Longest day15 h 56 mindaylight on June 21
Shortest day8 h 29 mindaylight on December 21
Onions to growLong-daysummer days reach 15+ hours, enough for long-day varieties (intermediate types work too)
Precipitation16.7 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 23 °F 37°23° JanFebruary: average high 40 °F, low 22 °F 40°22° FebMarch: average high 51 °F, low 28 °F 51°28° MarApril: average high 59 °F, low 34 °F 59°34° AprMay: average high 69 °F, low 41 °F 69°41° MayJune: average high 75 °F, low 47 °F 75°47° JunJuly: average high 86 °F, low 52 °F 86°52° JulAugust: average high 86 °F, low 51 °F 86°51° AugSeptember: average high 75 °F, low 44 °F 75°44° SepOctober: average high 59 °F, low 35 °F 59°35° OctNovember: average high 45 °F, low 28 °F 45°28° NovDecember: average high 37 °F, low 23 °F 37°23° Dec

Precipitation by month inches

0″1″2″3″January: 0.95 in precipitation 0.9 JanFebruary: 1.15 in precipitation 1.1 FebMarch: 0.94 in precipitation 0.9 MarApril: 1.75 in precipitation 1.8 AprMay: 2.30 in precipitation 2.3 MayJune: 2.63 in precipitation 2.6 JunJuly: 0.97 in precipitation 1.0 JulAugust: 1.17 in precipitation 1.2 AugSeptember: 1.51 in precipitation 1.5 SepOctober: 1.28 in precipitation 1.3 OctNovember: 1.13 in precipitation 1.1 NovDecember: 0.94 in precipitation 0.9 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Saint Ignatius, MT (8 mi away); precipitation: Saint Ignatius, MT (8 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

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

598656a
Saint Ignatius, MT · 9 mi
598636a
Ravalli, MT · 10 mi
598346a
Frenchtown, MT · 13 mi
598246a
Charlo, MT · 17 mi
598316a
Dixon, MT · 17 mi
598085b
Missoula, MT · 17 mi
598076a
Missoula, MT · 21 mi
598025b
Missoula, MT · 22 mi

Montana planting zones →

Questions about 59821

What planting zone is ZIP code 59821?

ZIP code 59821 (Arlee, 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 Arlee, MT?

The median last spring frost (32 °F) near 59821 is May 12; after June 1 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Saint Ignatius station.

When is the first frost in Arlee, MT?

The median first fall frost near 59821 is October 2, giving a median frost-free growing season of 142 days.

When should I plant tomatoes in 59821?

Start tomato seeds indoors around Mar 17 – Mar 31 and set transplants outside around May 19 – Jun 2, one to three weeks after the median last frost.

How much rain and snow does 59821 get?

About 16.7 inches of precipitation a year (NOAA 1991–2020 normals, Saint Ignatius station).

How hot do summers get in Arlee, MT?

The average high peaks at 86 °F in July, with about 20 days a year at 90 °F or more.

What kind of soil does 59821 have?

The USDA soil survey maps Repp at the center of ZIP 59821: mucky peat, well drained, pH about 6.5 (neutral).

Did spring come early in Arlee, MT in 2026?

Spring leaf-out near 59821 came on Apr 27 in 2026, 3 days earlier than the 1991–2020 average (Apr 30), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Arlee, MT?

Long-day onions: the longest day near 59821 is 15 h 56 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).