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

Planting zone for 59036 — Harlowton, MT

ZIP code 59036 (Harlowton, Wheatland County) is in USDA zone 4b: the coldest winter night averages −25 to −20 °F. The median last spring frost is May 23 and the first fall frost September 16.

Where ZIP 59036 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.

Zone4b−25 to −20 °F
Coldest night−31.7 to −28.9 °C
Last frostMay 23
First frostSep 16
2012 zone4b

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 4b means →

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for Harlowton, 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 Harlowton, MT

JanFebMarAprMayJunJulAugSepOctNovDec
Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free
Last spring frostMay 23median — 50% chance of a later frost
Safe for tender plantsJune 6only 10% chance of frost after
First fall frostSeptember 16median — 10% chance by Sep 1
Growing season113 daysfrost-free, median

A hard freeze (28 °F) usually ends around May 12 and returns around September 27.

From the NOAA station Harlowton, MT — 2 miles away, elevation 4,223 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 59036

JanFebMarAprMayJunJulAugSepOctNovDec
PeasSow outdoors · Apr 11 – Apr 25
SpinachSow outdoors · Apr 11 – May 2
Broccoli, cabbageStart indoors · Mar 14 – Mar 28
Broccoli, cabbageTransplant · May 2 – May 16
Onion setsPlant outdoors · Apr 25 – May 9
PotatoesPlant outdoors · May 2 – May 16
LettuceSow outdoors · Apr 25 – May 9
Carrots, beetsSow outdoors · May 2 – May 16
TomatoesStart indoors · Mar 28 – Apr 11
TomatoesTransplant · May 30 – Jun 13
Peppers, eggplantStart indoors · Mar 14 – Mar 28
Peppers, eggplantTransplant · Jun 6 – Jun 20
BeansSow outdoors · May 30 – Jun 13
Sweet cornSow outdoors · May 30 – Jun 13
Cucumbers, squashSow outdoors · May 30 – Jun 13
Fall lettuce, spinachSow outdoors · Jul 22 – Aug 5
GarlicPlant cloves · Sep 2 – Oct 7
Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (May 23) and first fall frost (Sep 16) 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 59036 came on Mar 15 — 29 days earlier than the 1991–2020 average (Apr 13).

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 4b in Montana

506 plants native to the lower 48 states, recorded in Montana, and rated by the USDA to survive −25 °F or colder — the bottom of zone 4b. Each links to its USDA PLANTS profile.

Trees 23

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 87

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 229

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 155

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 Harlowton, MT.

Soil in Harlowton, MT

The soil mapped at the center of ZIP 59036 is Crago — gravelly loam, well drained.

TextureGravelly loama good balance for most vegetables
pH8.2alkaline; most vegetables like 6.0–7.0
DrainageWell drainednatural drainage class
Organic matter2%moderate
Hydrologic groupBwater soaks in moderately
Farmland classNot prime farmlandUSDA classification

Map unit: Crago gravelly loam, 8 to 35 percent slopes, fan.

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 59036; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Harlowton, MT

Summer high84 °Faverage high, July
Winter low13 °Faverage low, January
Hot days21days a year at 90 °F or more
Freezing nights191nights a year at 32 °F or less
Growing degree days1,696base 50 °F — the season’s usable heat
Longest day15 h 49 mindaylight on June 21
Shortest day8 h 35 mindaylight on December 21
Onions to growLong-daysummer days reach 15+ hours, enough for long-day varieties (intermediate types work too)
Precipitation13.2 inper year, rain and melted snow
Snowfall20 inper year

Average high and low, by month

0°10°20°30°40°50°60°70°80°90°32 °FJanuary: average high 36 °F, low 13 °F 36°13° JanFebruary: average high 38 °F, low 14 °F 38°14° FebMarch: average high 48 °F, low 20 °F 48°20° MarApril: average high 54 °F, low 28 °F 54°28° AprMay: average high 64 °F, low 37 °F 64°37° MayJune: average high 74 °F, low 46 °F 74°46° JunJuly: average high 84 °F, low 50 °F 84°50° JulAugust: average high 83 °F, low 48 °F 83°48° AugSeptember: average high 73 °F, low 40 °F 73°40° SepOctober: average high 57 °F, low 30 °F 57°30° OctNovember: average high 45 °F, low 21 °F 45°21° NovDecember: average high 35 °F, low 15 °F 35°15° Dec

Precipitation by month inches · ❄ = snowfall

0″1″2″3″January: 0.31 in precipitation, 3.7 in snowfall 0.3❄4 JanFebruary: 0.30 in precipitation, 1.9 in snowfall 0.3❄2 FebMarch: 0.55 in precipitation, 2.6 in snowfall 0.6❄3 MarApril: 1.34 in precipitation, 3.1 in snowfall 1.3❄3 AprMay: 2.53 in precipitation, 0.3 in snowfall 2.5 MayJune: 2.81 in precipitation 2.8 JunJuly: 1.42 in precipitation 1.4 JulAugust: 1.25 in precipitation 1.3 AugSeptember: 1.07 in precipitation, 0.1 in snowfall 1.1 SepOctober: 0.68 in precipitation, 0.6 in snowfall 0.7❄1 OctNovember: 0.51 in precipitation, 3.6 in snowfall 0.5❄4 NovDecember: 0.41 in precipitation, 3.7 in snowfall 0.4❄4 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Harlowton, MT (2 mi away); precipitation: Harlowton, MT (2 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

All 8 nearest ZIP codes share zone 4b.

594534b
Judith Gap, MT · 16 mi
590854b
Two Dot, MT · 17 mi
590784b
Shawmut, MT · 19 mi
594184b
Buffalo, MT · 24 mi
590554b
Melville, MT · 25 mi
590534b
Martinsdale, MT · 26 mi
590744b
Ryegate, MT · 29 mi
594644b
Moore, MT · 29 mi

Montana planting zones →

Questions about 59036

What planting zone is ZIP code 59036?

ZIP code 59036 (Harlowton, MT) is in USDA hardiness zone 4b on the 2023 map: the coldest night of an average winter reaches −25 to −20 °F (−31.7 to −28.9 °C).

When is the last frost in Harlowton, MT?

The median last spring frost (32 °F) near 59036 is May 23; after June 6 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Harlowton station.

When is the first frost in Harlowton, MT?

The median first fall frost near 59036 is September 16, giving a median frost-free growing season of 113 days.

When should I plant tomatoes in 59036?

Start tomato seeds indoors around Mar 28 – Apr 11 and set transplants outside around May 30 – Jun 13, one to three weeks after the median last frost.

How much rain and snow does 59036 get?

About 13.2 inches of precipitation a year and 20 inches of snowfall (NOAA 1991–2020 normals, Harlowton station).

How hot do summers get in Harlowton, MT?

The average high peaks at 84 °F in July, with about 21 days a year at 90 °F or more.

What kind of soil does 59036 have?

The USDA soil survey maps Crago at the center of ZIP 59036: gravelly loam, well drained, pH about 8.2 (alkaline).

Did spring come early in Harlowton, MT in 2026?

Spring leaf-out near 59036 came on Mar 15 in 2026, 29 days earlier than the 1991–2020 average (Apr 13), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Harlowton, MT?

Long-day onions: the longest day near 59036 is 15 h 49 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).