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

Planting zone for 59223 — Fort Peck, MT

ZIP code 59223 (Fort Peck, Valley County) is in USDA zone 4a: the coldest winter night averages −30 to −25 °F. The median last spring frost is May 8 and the first fall frost October 1.

Where ZIP 59223 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 8
First frostOct 1
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 Peck, 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 Peck, MT

JanFebMarAprMayJunJulAugSepOctNovDec
Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free
Last spring frostMay 8median — 50% chance of a later frost
Safe for tender plantsMay 20only 10% chance of frost after
First fall frostOctober 1median — 10% chance by Sep 18
Growing season145 daysfrost-free, median

A hard freeze (28 °F) usually ends around April 28 and returns around October 10.

From the NOAA station Ft Peck Pwr Plt, MT — 12 miles away, elevation 2,070 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 59223

JanFebMarAprMayJunJulAugSepOctNovDec
PeasSow outdoors · Mar 27 – Apr 10
SpinachSow outdoors · Mar 27 – Apr 17
Broccoli, cabbageStart indoors · Feb 27 – Mar 13
Broccoli, cabbageTransplant · Apr 17 – May 1
Onion setsPlant outdoors · Apr 10 – Apr 24
PotatoesPlant outdoors · Apr 17 – May 1
LettuceSow outdoors · Apr 10 – Apr 24
Carrots, beetsSow outdoors · Apr 17 – May 1
TomatoesStart indoors · Mar 13 – Mar 27
TomatoesTransplant · May 15 – May 29
Peppers, eggplantStart indoors · Feb 27 – Mar 13
Peppers, eggplantTransplant · May 22 – Jun 5
BeansSow outdoors · May 15 – May 29
Sweet cornSow outdoors · May 15 – May 29
Cucumbers, squashSow outdoors · May 15 – May 29
Fall lettuce, spinachSow outdoors · Aug 6 – Aug 20
GarlicPlant cloves · Sep 17 – Oct 22
Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (May 8) and first fall frost (Oct 1) 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 59223 came on Apr 6 — 9 days earlier than the 1991–2020 average (Apr 15).

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 Peck, MT.

Soil in Fort Peck, MT

The soil mapped at the center of ZIP 59223 is Busby — fine sandy loam, well drained.

TextureFine sandy loamdrains and warms fast; dries out and needs more feeding
pH7.9alkaline; most vegetables like 6.0–7.0
DrainageWell drainednatural drainage class
Organic matter1.5%low — add compost
Hydrologic groupAwater soaks in fast
Farmland classNot prime farmlandUSDA classification

Map unit: Busby-Yamac-Fleak complex, 15 to 45 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 59223; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Fort Peck, MT

Summer high89 °Faverage high, July
Winter low8 °Faverage low, January
Hot days38days a year at 90 °F or more
Freezing nights164nights a year at 32 °F or less
Growing degree days2,728base 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)
Precipitation13.6 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 28 °F, low 8 °F 28°8° JanFebruary: average high 33 °F, low 12 °F 33°12° FebMarch: average high 46 °F, low 22 °F 46°22° MarApril: average high 60 °F, low 34 °F 60°34° AprMay: average high 71 °F, low 44 °F 71°44° MayJune: average high 80 °F, low 53 °F 80°53° JunJuly: average high 89 °F, low 59 °F 89°59° JulAugust: average high 88 °F, low 57 °F 88°57° AugSeptember: average high 77 °F, low 48 °F 77°48° SepOctober: average high 61 °F, low 37 °F 61°37° OctNovember: average high 44 °F, low 24 °F 44°24° NovDecember: average high 32 °F, low 13 °F 32°13° Dec

Precipitation by month inches

0″1″2″3″January: 0.30 in precipitation 0.3 JanFebruary: 0.30 in precipitation 0.3 FebMarch: 0.38 in precipitation 0.4 MarApril: 0.92 in precipitation 0.9 AprMay: 2.52 in precipitation 2.5 MayJune: 2.67 in precipitation 2.7 JunJuly: 2.39 in precipitation 2.4 JulAugust: 1.40 in precipitation 1.4 AugSeptember: 1.05 in precipitation 1.1 SepOctober: 0.94 in precipitation 0.9 OctNovember: 0.36 in precipitation 0.4 NovDecember: 0.35 in precipitation 0.3 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Ft Peck Pwr Plt, MT (12 mi away); precipitation: Ft Peck Pwr Plt, MT (12 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

All 8 nearest ZIP codes share zone 4a.

592484a
Nashua, MT · 23 mi
592254a
Frazer, MT · 27 mi
592014a
Wolf Point, MT · 31 mi
592304a
Glasgow, MT · 31 mi
592154a
Circle, MT · 34 mi
592744a
Vida, MT · 37 mi
592314a
Saint Marie, MT · 37 mi
592144a
Brockway, MT · 43 mi

Montana planting zones →

Questions about 59223

What planting zone is ZIP code 59223?

ZIP code 59223 (Fort Peck, 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 Peck, MT?

The median last spring frost (32 °F) near 59223 is May 8; after May 20 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Ft Peck Pwr Plt station.

When is the first frost in Fort Peck, MT?

The median first fall frost near 59223 is October 1, giving a median frost-free growing season of 145 days.

When should I plant tomatoes in 59223?

Start tomato seeds indoors around Mar 13 – Mar 27 and set transplants outside around May 15 – May 29, one to three weeks after the median last frost.

How much rain and snow does 59223 get?

About 13.6 inches of precipitation a year (NOAA 1991–2020 normals, Ft Peck Pwr Plt station).

How hot do summers get in Fort Peck, MT?

The average high peaks at 89 °F in July, with about 38 days a year at 90 °F or more.

What kind of soil does 59223 have?

The USDA soil survey maps Busby at the center of ZIP 59223: fine sandy loam, well drained, pH about 7.9 (alkaline).

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

Spring leaf-out near 59223 came on Apr 6 in 2026, 9 days earlier than the 1991–2020 average (Apr 15), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Fort Peck, MT?

Long-day onions: the longest day near 59223 is 16 h 02 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).