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

Planting zone for 59345 — Powderville, MT

ZIP code 59345 (Powderville, Powder River County) is in USDA zone 4b: the coldest winter night averages −25 to −20 °F. The median last spring frost is May 13 and the first fall frost September 25.

Where ZIP 59345 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 13
First frostSep 25
2012 zone4a

Was 4a 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 4b means →

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for Powderville, 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 Powderville, MT

JanFebMarAprMayJunJulAugSepOctNovDec
Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free
Last spring frostMay 13median — 50% chance of a later frost
Safe for tender plantsMay 31only 10% chance of frost after
First fall frostSeptember 25median — 10% chance by Sep 6
Growing season132 daysfrost-free, median

A hard freeze (28 °F) usually ends around May 2 and returns around October 4.

From the NOAA station Powderville 8 Nne, MT — 9 miles away, elevation 2,799 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 59345

JanFebMarAprMayJunJulAugSepOctNovDec
PeasSow outdoors · Apr 1 – Apr 15
SpinachSow outdoors · Apr 1 – Apr 22
Broccoli, cabbageStart indoors · Mar 4 – Mar 18
Broccoli, cabbageTransplant · Apr 22 – May 6
Onion setsPlant outdoors · Apr 15 – Apr 29
PotatoesPlant outdoors · Apr 22 – May 6
LettuceSow outdoors · Apr 15 – Apr 29
Carrots, beetsSow outdoors · Apr 22 – May 6
TomatoesStart indoors · Mar 18 – Apr 1
TomatoesTransplant · May 20 – Jun 3
Peppers, eggplantStart indoors · Mar 4 – Mar 18
Peppers, eggplantTransplant · May 27 – Jun 10
BeansSow outdoors · May 20 – Jun 3
Sweet cornSow outdoors · May 20 – Jun 3
Cucumbers, squashSow outdoors · May 20 – Jun 3
Fall lettuce, spinachSow outdoors · Jul 31 – Aug 14
GarlicPlant cloves · Sep 11 – Oct 16
Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (May 13) and first fall frost (Sep 25) 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 59345 came on Mar 23 — 18 days earlier than the 1991–2020 average (Apr 10).

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).

Soil in Powderville, MT

The soil mapped at the center of ZIP 59345 is Yamacall — loam, well drained.

TextureLoama good balance for most vegetables
pH7.5slightly alkaline; 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: Yamacall-Delpoint-Cabbart loams, 4 to 15 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 59345; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Powderville, MT

Summer high90 °Faverage high, July
Winter low10 °Faverage low, January
Hot days45days a year at 90 °F or more
Freezing nights179nights a year at 32 °F or less
Growing degree days2,704base 50 °F — the season’s usable heat
Longest day15 h 44 mindaylight on June 21
Shortest day8 h 39 mindaylight on December 21
Onions to growLong-daysummer days reach 15+ hours, enough for long-day varieties (intermediate types work too)
Precipitation15 inper year, rain and melted snow
Snowfall30 inper year; 67 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 32 °F, low 10 °F 32°10° JanFebruary: average high 36 °F, low 14 °F 36°14° FebMarch: average high 49 °F, low 23 °F 49°23° MarApril: average high 59 °F, low 33 °F 59°33° AprMay: average high 70 °F, low 43 °F 70°43° MayJune: average high 80 °F, low 52 °F 80°52° JunJuly: average high 90 °F, low 59 °F 90°59° JulAugust: average high 89 °F, low 57 °F 89°57° AugSeptember: average high 78 °F, low 46 °F 78°46° SepOctober: average high 61 °F, low 34 °F 61°34° OctNovember: average high 46 °F, low 21 °F 46°21° NovDecember: average high 35 °F, low 12 °F 35°12° Dec

Precipitation by month inches · ❄ = snowfall

0″1″2″3″January: 0.43 in precipitation, 5.4 in snowfall 0.4❄5 JanFebruary: 0.51 in precipitation, 5.8 in snowfall 0.5❄6 FebMarch: 0.74 in precipitation, 5.1 in snowfall 0.7❄5 MarApril: 1.64 in precipitation, 2.6 in snowfall 1.6❄3 AprMay: 2.84 in precipitation, 1.1 in snowfall 2.8❄1 MayJune: 2.68 in precipitation 2.7 JunJuly: 1.72 in precipitation 1.7 JulAugust: 1.23 in precipitation 1.2 AugSeptember: 1.25 in precipitation 1.3 SepOctober: 1.16 in precipitation, 1.7 in snowfall 1.2❄2 OctNovember: 0.47 in precipitation, 3.3 in snowfall 0.5❄3 NovDecember: 0.35 in precipitation, 4.9 in snowfall 0.3❄5 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Powderville 8 Nne, MT (9 mi away); precipitation: Powderville 8 Nne, MT (9 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

1 of the 8 nearest ZIP codes are in a different zone — elevation and distance from water change winter lows quickly.

593434b
Olive, MT · 17 mi
593514b
Volborg, MT · 25 mi
593244b
Ekalaka, MT · 32 mi
593364a
Ismay, MT · 36 mi
593164b
Boyes, MT · 36 mi
593174b
Broadus, MT · 39 mi
593324b
Hammond, MT · 41 mi
593544b
Willard, MT · 44 mi

Montana planting zones →

Questions about 59345

What planting zone is ZIP code 59345?

ZIP code 59345 (Powderville, 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 Powderville, MT?

The median last spring frost (32 °F) near 59345 is May 13; after May 31 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Powderville 8 Nne station.

When is the first frost in Powderville, MT?

The median first fall frost near 59345 is September 25, giving a median frost-free growing season of 132 days.

When should I plant tomatoes in 59345?

Start tomato seeds indoors around Mar 18 – Apr 1 and set transplants outside around May 20 – Jun 3, one to three weeks after the median last frost.

How much rain and snow does 59345 get?

About 15 inches of precipitation a year and 30 inches of snowfall (NOAA 1991–2020 normals, Powderville 8 Nne station).

How hot do summers get in Powderville, MT?

The average high peaks at 90 °F in July, with about 45 days a year at 90 °F or more.

What kind of soil does 59345 have?

The USDA soil survey maps Yamacall at the center of ZIP 59345: loam, well drained, pH about 7.5 (slightly alkaline).

Did spring come early in Powderville, MT in 2026?

Spring leaf-out near 59345 came on Mar 23 in 2026, 18 days earlier than the 1991–2020 average (Apr 10), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Powderville, MT?

Long-day onions: the longest day near 59345 is 15 h 44 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).

Did the zone for 59345 change?

Yes. The 2012 USDA map put 59345 in zone 4a; the 2023 map puts it in zone 4b. The newer map uses 1991–2020 data and more weather stations.