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

Planting zone for 59029 — Fromberg, MT

ZIP code 59029 (Fromberg, Carbon County) is in USDA zone 5a: the coldest winter night averages −20 to −15 °F. The median last spring frost is May 14 and the first fall frost September 24.

Where ZIP 59029 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.

Zone5a−20 to −15 °F
Coldest night−28.9 to −26.1 °C
Last frostMay 14
First frostSep 24
2012 zone4b

Was 4b on the 2012 map — half a zone warmer now. 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 Fromberg, 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 Fromberg, MT

JanFebMarAprMayJunJulAugSepOctNovDec
Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free
Last spring frostMay 14median — 50% chance of a later frost
Safe for tender plantsMay 30only 10% chance of frost after
First fall frostSeptember 24median — 10% chance by Sep 7
Growing season129 daysfrost-free, median

A hard freeze (28 °F) usually ends around May 1 and returns around October 4.

From the NOAA station Bridger 2 N, MT — 7 miles away, elevation 3,583 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 59029

JanFebMarAprMayJunJulAugSepOctNovDec
PeasSow outdoors · Apr 2 – Apr 16
SpinachSow outdoors · Apr 2 – Apr 23
Broccoli, cabbageStart indoors · Mar 5 – Mar 19
Broccoli, cabbageTransplant · Apr 23 – May 7
Onion setsPlant outdoors · Apr 16 – Apr 30
PotatoesPlant outdoors · Apr 23 – May 7
LettuceSow outdoors · Apr 16 – Apr 30
Carrots, beetsSow outdoors · Apr 23 – May 7
TomatoesStart indoors · Mar 19 – Apr 2
TomatoesTransplant · May 21 – Jun 4
Peppers, eggplantStart indoors · Mar 5 – Mar 19
Peppers, eggplantTransplant · May 28 – Jun 11
BeansSow outdoors · May 21 – Jun 4
Sweet cornSow outdoors · May 21 – Jun 4
Cucumbers, squashSow outdoors · May 21 – Jun 4
Fall lettuce, spinachSow outdoors · Jul 30 – Aug 13
GarlicPlant cloves · Sep 10 – Oct 15
Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (May 14) and first fall frost (Sep 24) 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 59029 came on Mar 5 — 33 days earlier than the 1991–2020 average (Apr 7).

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 Fromberg, MT.

Soil in Fromberg, MT

The soil mapped at the center of ZIP 59029 is Absarokee — clay loam, well drained.

TextureClay loamholds water and nutrients; slow to drain and warm up
pH6.7neutral; most vegetables like 6.0–7.0
DrainageWell drainednatural drainage class
Organic matter4.5%moderate
Hydrologic groupCwater soaks in slowly
Farmland classFarmland of local importanceUSDA classification

Map unit: Absarokee-Sinnigam clay loams, 4 to 8 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 59029; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Fromberg, MT

Summer high87 °Faverage high, July
Winter low13 °Faverage low, January
Hot days35days a year at 90 °F or more
Freezing nights179nights a year at 32 °F or less
Growing degree days2,121base 50 °F — the season’s usable heat
Longest day15 h 40 mindaylight on June 21
Shortest day8 h 43 mindaylight on December 21
Onions to growLong-daysummer days reach 15+ hours, enough for long-day varieties (intermediate types work too)
Precipitation13.8 inper year, rain and melted snow

Average high and low, by month

0°10°20°30°40°50°60°70°80°90°100°32 °FJanuary: average high 35 °F, low 13 °F 35°13° JanFebruary: average high 39 °F, low 15 °F 39°15° FebMarch: average high 50 °F, low 22 °F 50°22° MarApril: average high 58 °F, low 30 °F 58°30° AprMay: average high 67 °F, low 40 °F 67°40° MayJune: average high 77 °F, low 47 °F 77°47° JunJuly: average high 87 °F, low 53 °F 87°53° JulAugust: average high 86 °F, low 50 °F 86°50° AugSeptember: average high 75 °F, low 42 °F 75°42° SepOctober: average high 60 °F, low 32 °F 60°32° OctNovember: average high 46 °F, low 22 °F 46°22° NovDecember: average high 36 °F, low 14 °F 36°14° Dec

Precipitation by month inches

0″1″2″3″January: 0.40 in precipitation 0.4 JanFebruary: 0.38 in precipitation 0.4 FebMarch: 0.42 in precipitation 0.4 MarApril: 1.71 in precipitation 1.7 AprMay: 2.72 in precipitation 2.7 MayJune: 2.30 in precipitation 2.3 JunJuly: 1.24 in precipitation 1.2 JulAugust: 0.68 in precipitation 0.7 AugSeptember: 1.34 in precipitation 1.3 SepOctober: 1.59 in precipitation 1.6 OctNovember: 0.58 in precipitation 0.6 NovDecember: 0.47 in precipitation 0.5 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Bridger 2 N, MT (7 mi away); precipitation: Fromberg 2.7 Ne, MT (4 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

All 8 nearest ZIP codes share zone 5a.

590265a
Edgar, MT · 6 mi
590415a
Joliet, MT · 11 mi
590135a
Boyd, MT · 14 mi
590665a
Pryor, MT · 15 mi
590445a
Laurel, MT · 17 mi
590145a
Bridger, MT · 18 mi
590705a
Roberts, MT · 19 mi
590635a
Park City, MT · 19 mi

Montana planting zones →

Questions about 59029

What planting zone is ZIP code 59029?

ZIP code 59029 (Fromberg, 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 Fromberg, MT?

The median last spring frost (32 °F) near 59029 is May 14; after May 30 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Bridger 2 N station.

When is the first frost in Fromberg, MT?

The median first fall frost near 59029 is September 24, giving a median frost-free growing season of 129 days.

When should I plant tomatoes in 59029?

Start tomato seeds indoors around Mar 19 – Apr 2 and set transplants outside around May 21 – Jun 4, one to three weeks after the median last frost.

How much rain and snow does 59029 get?

About 13.8 inches of precipitation a year (NOAA 1991–2020 normals, Fromberg 2.7 Ne station).

How hot do summers get in Fromberg, MT?

The average high peaks at 87 °F in July, with about 35 days a year at 90 °F or more.

What kind of soil does 59029 have?

The USDA soil survey maps Absarokee at the center of ZIP 59029: clay loam, well drained, pH about 6.7 (neutral).

Did spring come early in Fromberg, MT in 2026?

Spring leaf-out near 59029 came on Mar 5 in 2026, 33 days earlier than the 1991–2020 average (Apr 7), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Fromberg, MT?

Long-day onions: the longest day near 59029 is 15 h 40 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).

Did the zone for 59029 change?

Yes. The 2012 USDA map put 59029 in zone 4b; the 2023 map puts it in zone 5a. The newer map uses 1991–2020 data and more weather stations.