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

Planting zone for 59915 — Elmo, MT

ZIP code 59915 (Elmo, Lake County) is in USDA zone 6a: the coldest winter night averages −10 to −5 °F. The median last spring frost is May 15 and the first fall frost September 28.

Where ZIP 59915 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.

Zone6a−10 to −5 °F
Coldest night−23.3 to −20.6 °C
Last frostMay 15
First frostSep 28
2012 zone6a

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 6a means →

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for Elmo, 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 Elmo, MT

JanFebMarAprMayJunJulAugSepOctNovDec
Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free
Last spring frostMay 15median — 50% chance of a later frost
Safe for tender plantsJune 1only 10% chance of frost after
First fall frostSeptember 28median — 10% chance by Sep 13
Growing season134 daysfrost-free, median

A hard freeze (28 °F) usually ends around May 2 and returns around October 8.

From the NOAA station Skq Dam, MT — 12 miles away, elevation 2,730 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 59915

JanFebMarAprMayJunJulAugSepOctNovDec
PeasSow outdoors · Apr 3 – Apr 17
SpinachSow outdoors · Apr 3 – Apr 24
Broccoli, cabbageStart indoors · Mar 6 – Mar 20
Broccoli, cabbageTransplant · Apr 24 – May 8
Onion setsPlant outdoors · Apr 17 – May 1
PotatoesPlant outdoors · Apr 24 – May 8
LettuceSow outdoors · Apr 17 – May 1
Carrots, beetsSow outdoors · Apr 24 – May 8
TomatoesStart indoors · Mar 20 – Apr 3
TomatoesTransplant · May 22 – Jun 5
Peppers, eggplantStart indoors · Mar 6 – Mar 20
Peppers, eggplantTransplant · May 29 – Jun 12
BeansSow outdoors · May 22 – Jun 5
Sweet cornSow outdoors · May 22 – Jun 5
Cucumbers, squashSow outdoors · May 22 – Jun 5
Fall lettuce, spinachSow outdoors · Aug 3 – Aug 17
GarlicPlant cloves · Sep 14 – Oct 19
Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (May 15) and first fall frost (Sep 28) 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 59915 came on Apr 12 — 7 days earlier than the 1991–2020 average (Apr 19).

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 6a in Montana

572 plants native to the lower 48 states, recorded in Montana, and rated by the USDA to survive −10 °F or colder — the bottom of zone 6a. 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 100

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 266

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 Elmo, MT.

Soil in Elmo, MT

The soil mapped at the center of ZIP 59915 is Niarada — gravelly loam, well drained.

TextureGravelly loama good balance for most vegetables
pH6.7neutral; most vegetables like 6.0–7.0
DrainageWell drainednatural drainage class
Organic matter4%moderate
Hydrologic groupBwater soaks in moderately
Farmland classNot prime farmlandUSDA classification

Map unit: Niarada gravelly loam, cool, 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 59915; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Elmo, MT

Summer high83 °Faverage high, July
Winter low20 °Faverage low, January
Hot days18days a year at 90 °F or more
Freezing nights153nights a year at 32 °F or less
Growing degree days1,751base 50 °F — the season’s usable heat
Longest day16 h 01 mindaylight on June 21
Shortest day8 h 24 mindaylight on December 21
Onions to growLong-daysummer days reach 15+ hours, enough for long-day varieties (intermediate types work too)
Precipitation25 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 32 °F, low 20 °F 32°20° JanFebruary: average high 37 °F, low 21 °F 37°21° FebMarch: average high 47 °F, low 26 °F 47°26° MarApril: average high 56 °F, low 32 °F 56°32° AprMay: average high 65 °F, low 40 °F 65°40° MayJune: average high 71 °F, low 46 °F 71°46° JunJuly: average high 83 °F, low 52 °F 83°52° JulAugust: average high 83 °F, low 51 °F 83°51° AugSeptember: average high 71 °F, low 43 °F 71°43° SepOctober: average high 55 °F, low 34 °F 55°34° OctNovember: average high 40 °F, low 26 °F 40°26° NovDecember: average high 32 °F, low 21 °F 32°21° Dec

Precipitation by month inches

0″1″2″3″January: 2.17 in precipitation 2.2 JanFebruary: 2.11 in precipitation 2.1 FebMarch: 1.88 in precipitation 1.9 MarApril: 2.64 in precipitation 2.6 AprMay: 2.21 in precipitation 2.2 MayJune: 2.90 in precipitation 2.9 JunJuly: 1.07 in precipitation 1.1 JulAugust: 1.12 in precipitation 1.1 AugSeptember: 1.50 in precipitation 1.5 SepOctober: 2.27 in precipitation 2.3 OctNovember: 2.35 in precipitation 2.4 NovDecember: 2.79 in precipitation 2.8 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Skq Dam, MT (12 mi away); precipitation: Blacktail Mtn, MT (11 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

All 8 nearest ZIP codes share zone 6a.

599146a
Dayton, MT · 6 mi
599296a
Proctor, MT · 7 mi
599106a
Big Arm, MT · 8 mi
599316a
Rollins, MT · 10 mi
598456a
Hot Springs, MT · 11 mi
598606a
Polson, MT · 13 mi
598486a
Lonepine, MT · 15 mi
599226a
Lakeside, MT · 15 mi

Montana planting zones →

Questions about 59915

What planting zone is ZIP code 59915?

ZIP code 59915 (Elmo, MT) is in USDA hardiness zone 6a on the 2023 map: the coldest night of an average winter reaches −10 to −5 °F (−23.3 to −20.6 °C).

When is the last frost in Elmo, MT?

The median last spring frost (32 °F) near 59915 is May 15; after June 1 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Skq Dam station.

When is the first frost in Elmo, MT?

The median first fall frost near 59915 is September 28, giving a median frost-free growing season of 134 days.

When should I plant tomatoes in 59915?

Start tomato seeds indoors around Mar 20 – Apr 3 and set transplants outside around May 22 – Jun 5, one to three weeks after the median last frost.

How much rain and snow does 59915 get?

About 25 inches of precipitation a year (NOAA 1991–2020 normals, Blacktail Mtn station).

How hot do summers get in Elmo, MT?

The average high peaks at 83 °F in July, with about 18 days a year at 90 °F or more.

What kind of soil does 59915 have?

The USDA soil survey maps Niarada at the center of ZIP 59915: gravelly loam, well drained, pH about 6.7 (neutral).

Did spring come early in Elmo, MT in 2026?

Spring leaf-out near 59915 came on Apr 12 in 2026, 7 days earlier than the 1991–2020 average (Apr 19), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Elmo, MT?

Long-day onions: the longest day near 59915 is 16 h 01 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).