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

Planting zone for 59442 — Fort Benton, MT

ZIP code 59442 (Fort Benton, Chouteau County) is in USDA zone 4a: the coldest winter night averages −30 to −25 °F. The median last spring frost is May 15 and the first fall frost September 22.

Where ZIP 59442 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.

Zone4a−30 to −25 °F
Coldest night−34.4 to −31.7 °C
Last frostMay 15
First frostSep 22
2012 zone4a

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 4a means →

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for Fort Benton, 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 Fort Benton, 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 plantsMay 30only 10% chance of frost after
First fall frostSeptember 22median — 10% chance by Sep 7
Growing season129 daysfrost-free, median

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

From the NOAA station Ft Benton, MT — 7 miles away, elevation 2,648 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 59442

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 · Jul 28 – Aug 11
GarlicPlant cloves · Sep 8 – Oct 13
Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (May 15) and first fall frost (Sep 22) 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 59442 came on Mar 16 — 24 days earlier than the 1991–2020 average (Apr 9).

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 4a in Montana

439 plants native to the lower 48 states, recorded in Montana, and rated by the USDA to survive −30 °F or colder — the bottom of zone 4a. Each links to its USDA PLANTS profile.

Trees 21

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 77

alderleaf buckthorn3 ft · blooms late spring · low shade tolerance · to −33 °Falderleaf mountain mahogany15 ft · blooms late spring · medium shade tolerance · to −41 °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 °FBarclay's willow15 ft · high shade tolerance · to −43 °F

Wildflowers & perennials 189

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 bistort1.5 ft · blooms mid spring · high shade tolerance · to −38 °FAmerican licorice4 ft · blooms late spring · medium shade tolerance · to −38 °F

Grasses 141

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 Fort Benton, MT.

Soil in Fort Benton, MT

The soil mapped at the center of ZIP 59442 is Chinook — fine sandy loam, well drained.

TextureFine sandy loamdrains and warms fast; dries out and needs more feeding
pH7.0neutral; most vegetables like 6.0–7.0
DrainageWell drainednatural drainage class
Organic matter2%moderate
Hydrologic groupAwater soaks in fast
Farmland classFarmland of statewide importanceUSDA classification

Map unit: Chinook fine sandy loam, 0 to 4 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 59442; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Fort Benton, MT

Summer high86 °Faverage high, July
Winter low10 °Faverage low, January
Hot days31days a year at 90 °F or more
Freezing nights173nights a year at 32 °F or less
Growing degree days2,164base 50 °F — the season’s usable heat
Longest day16 h 02 mindaylight on June 21
Shortest day8 h 23 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
Snowfall38 inper year; 50 days with snow on the ground

Average high and low, by month

0°10°20°30°40°50°60°70°80°90°100°32 °FJanuary: average high 35 °F, low 10 °F 35°10° JanFebruary: average high 38 °F, low 13 °F 38°13° FebMarch: average high 48 °F, low 20 °F 48°20° MarApril: average high 59 °F, low 31 °F 59°31° AprMay: average high 68 °F, low 41 °F 68°41° MayJune: average high 76 °F, low 49 °F 76°49° JunJuly: average high 86 °F, low 54 °F 86°54° JulAugust: average high 86 °F, low 52 °F 86°52° AugSeptember: average high 74 °F, low 42 °F 74°42° SepOctober: average high 60 °F, low 31 °F 60°31° OctNovember: average high 47 °F, low 21 °F 47°21° NovDecember: average high 37 °F, low 13 °F 37°13° Dec

Precipitation by month inches · ❄ = snowfall

0″1″2″3″January: 0.52 in precipitation, 7.9 in snowfall 0.5❄8 JanFebruary: 0.44 in precipitation, 6.9 in snowfall 0.4❄7 FebMarch: 0.56 in precipitation, 4.3 in snowfall 0.6❄4 MarApril: 1.48 in precipitation, 3 in snowfall 1.5❄3 AprMay: 2.08 in precipitation, 0.3 in snowfall 2.1 MayJune: 2.62 in precipitation 2.6 JunJuly: 1.19 in precipitation 1.2 JulAugust: 1.16 in precipitation 1.2 AugSeptember: 1.20 in precipitation, 0.3 in snowfall 1.2 SepOctober: 0.92 in precipitation, 1.9 in snowfall 0.9❄2 OctNovember: 0.58 in precipitation, 5.7 in snowfall 0.6❄6 NovDecember: 0.47 in precipitation, 7.9 in snowfall 0.5❄8 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Ft Benton, MT (7 mi away); precipitation: Ft Benton, MT (7 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.

594604a
Loma, MT · 12 mi
594204a
Carter, MT · 17 mi
594504b
Highwood, MT · 26 mi
594404b
Floweree, MT · 28 mi
594464b
Geraldine, MT · 30 mi
594064b
Great Falls, MT · 35 mi
594124b
Belt, MT · 44 mi
594474b
Geyser, MT · 45 mi

Montana planting zones →

Questions about 59442

What planting zone is ZIP code 59442?

ZIP code 59442 (Fort Benton, MT) is in USDA hardiness zone 4a on the 2023 map: the coldest night of an average winter reaches −30 to −25 °F (−34.4 to −31.7 °C).

When is the last frost in Fort Benton, MT?

The median last spring frost (32 °F) near 59442 is May 15; after May 30 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Ft Benton station.

When is the first frost in Fort Benton, MT?

The median first fall frost near 59442 is September 22, giving a median frost-free growing season of 129 days.

When should I plant tomatoes in 59442?

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 59442 get?

About 13.2 inches of precipitation a year and 38 inches of snowfall (NOAA 1991–2020 normals, Ft Benton station).

How hot do summers get in Fort Benton, MT?

The average high peaks at 86 °F in July, with about 31 days a year at 90 °F or more.

What kind of soil does 59442 have?

The USDA soil survey maps Chinook at the center of ZIP 59442: fine sandy loam, well drained, pH about 7.0 (neutral).

Did spring come early in Fort Benton, MT in 2026?

Spring leaf-out near 59442 came on Mar 16 in 2026, 24 days earlier than the 1991–2020 average (Apr 9), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Fort Benton, MT?

Long-day onions: the longest day near 59442 is 16 h 02 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).