Data: 2023 USDA zones (PRISM/OSU) · NOAA 1991–2020 normals · updated Oct 29, 2026

Planting zone for 59250 — Opheim, MT

ZIP code 59250 (Opheim, Valley County) is in USDA zone 3b: the coldest winter night averages −35 to −30 °F. The median last spring frost is June 1 and the first fall frost September 7.

Where ZIP 59250 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.

Zone3b−35 to −30 °F

Coldest night−37.2 to −34.4 °C

Last frostJun 1

First frostSep 7

2012 zone3b

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 3b means →

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for Opheim, 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 Opheim, MT

JanFebMarAprMayJunJulAugSepOctNovDec

Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free

Last spring frostJune 1median — 50% chance of a later frost

Safe for tender plantsJune 18only 10% chance of frost after

First fall frostSeptember 7median — 10% chance by Aug 24

Growing season99 daysfrost-free, median

A hard freeze (28 °F) usually ends around May 21 and returns around September 19.

From the NOAA station Opheim 10 N, MT — 16 miles away, elevation 2,877 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 59250

JanFebMarAprMayJunJulAugSepOctNovDec

PeasSow outdoors · Apr 20 – May 4

SpinachSow outdoors · Apr 20 – May 11

Broccoli, cabbageStart indoors · Mar 23 – Apr 6

Broccoli, cabbageTransplant · May 11 – May 25

Onion setsPlant outdoors · May 4 – May 18

PotatoesPlant outdoors · May 11 – May 25

LettuceSow outdoors · May 4 – May 18

Carrots, beetsSow outdoors · May 11 – May 25

TomatoesStart indoors · Apr 6 – Apr 20

TomatoesTransplant · Jun 8 – Jun 22

Peppers, eggplantStart indoors · Mar 23 – Apr 6

Peppers, eggplantTransplant · Jun 15 – Jun 29

BeansSow outdoors · Jun 8 – Jun 22

Sweet cornSow outdoors · Jun 8 – Jun 22

Cucumbers, squashSow outdoors · Jun 8 – Jun 22

Fall lettuce, spinachSow outdoors · Jul 13 – Jul 27

GarlicPlant cloves · Aug 24 – Sep 28

Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (Jun 1) and first fall frost (Sep 7) 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 59250 came on Apr 24 — about the same time as the 1991–2020 average (Apr 24).

average
Apr 242026
Apr 24

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 3b in Montana

304 plants native to the lower 48 states, recorded in Montana, and rated by the USDA to survive −35 °F or colder — the bottom of zone 3b. Each links to its USDA PLANTS profile.

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 Opheim, MT.

Soil in Opheim, MT

The soil mapped at the center of ZIP 59250 is Reeder — loam, well drained.

TextureLoama good balance for most vegetables

pH7.0neutral; most vegetables like 6.0–7.0

DrainageWell drainednatural drainage class

Organic matter3%moderate

Hydrologic groupCwater soaks in slowly

Farmland classNot prime farmlandUSDA classification

Map unit: Reeder-Doney-Cambert complex, 9 to 35 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 59250; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Opheim, MT

Summer high81 °Faverage high, July

Winter low1 °Faverage low, January

Hot days12days a year at 90 °F or more

Freezing nights210nights a year at 32 °F or less

Growing degree days1,599base 50 °F — the season’s usable heat

Longest day16 h 11 mindaylight on June 21

Shortest day8 h 15 mindaylight on December 21

Onions to growLong-daysummer days reach 15+ hours, enough for long-day varieties (intermediate types work too)

Precipitation14.4 inper year, rain and melted snow

Snowfall33 inper year

Average high and low, by month

Precipitation by month inches · ❄ = snowfall

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Opheim 10 N, MT (16 mi away); precipitation: Opheim 10 N, MT (16 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

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

Saint Marie, MT · 31 mi

Montana planting zones →

Questions about 59250

What planting zone is ZIP code 59250?

ZIP code 59250 (Opheim, MT) is in USDA hardiness zone 3b on the 2023 map: the coldest night of an average winter reaches −35 to −30 °F (−37.2 to −34.4 °C).

When is the last frost in Opheim, MT?

The median last spring frost (32 °F) near 59250 is June 1; after June 18 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Opheim 10 N station.

When is the first frost in Opheim, MT?

The median first fall frost near 59250 is September 7, giving a median frost-free growing season of 99 days.

When should I plant tomatoes in 59250?

Start tomato seeds indoors around Apr 6 – Apr 20 and set transplants outside around Jun 8 – Jun 22, one to three weeks after the median last frost.

How much rain and snow does 59250 get?

About 14.4 inches of precipitation a year and 33 inches of snowfall (NOAA 1991–2020 normals, Opheim 10 N station).

How hot do summers get in Opheim, MT?

The average high peaks at 81 °F in July, with about 12 days a year at 90 °F or more.

What kind of soil does 59250 have?

The USDA soil survey maps Reeder at the center of ZIP 59250: loam, well drained, pH about 7.0 (neutral).

Did spring come early in Opheim, MT in 2026?

Spring leaf-out near 59250 came on Apr 24 in 2026, about the same as the 1991–2020 average (Apr 24), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Opheim, MT?

Long-day onions: the longest day near 59250 is 16 h 11 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).