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

Planting zone for 59322 — Cohagen, MT

ZIP code 59322 (Cohagen, Garfield County) is in USDA zone 4a: the coldest winter night averages −30 to −25 °F. The median last spring frost is May 25 and the first fall frost September 14.

Where ZIP 59322 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 25

First frostSep 14

2012 zone3b

Was 3b 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 4a means →

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for Cohagen, 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 Cohagen, MT

JanFebMarAprMayJunJulAugSepOctNovDec

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

Last spring frostMay 25median — 50% chance of a later frost

Safe for tender plantsJune 9only 10% chance of frost after

First fall frostSeptember 14median — 10% chance by Aug 31

Growing season110 daysfrost-free, median

A hard freeze (28 °F) usually ends around May 16 and returns around September 23.

From the NOAA station Cohagen, MT — 4 miles away, elevation 2,720 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 59322

JanFebMarAprMayJunJulAugSepOctNovDec

PeasSow outdoors · Apr 13 – Apr 27

SpinachSow outdoors · Apr 13 – May 4

Broccoli, cabbageStart indoors · Mar 16 – Mar 30

Broccoli, cabbageTransplant · May 4 – May 18

Onion setsPlant outdoors · Apr 27 – May 11

PotatoesPlant outdoors · May 4 – May 18

LettuceSow outdoors · Apr 27 – May 11

Carrots, beetsSow outdoors · May 4 – May 18

TomatoesStart indoors · Mar 30 – Apr 13

TomatoesTransplant · Jun 1 – Jun 15

Peppers, eggplantStart indoors · Mar 16 – Mar 30

Peppers, eggplantTransplant · Jun 8 – Jun 22

BeansSow outdoors · Jun 1 – Jun 15

Sweet cornSow outdoors · Jun 1 – Jun 15

Cucumbers, squashSow outdoors · Jun 1 – Jun 15

Fall lettuce, spinachSow outdoors · Jul 20 – Aug 3

GarlicPlant cloves · Aug 31 – Oct 5

Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (May 25) and first fall frost (Sep 14) 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 59322 came on Mar 23 — 20 days earlier than the 1991–2020 average (Apr 12).

average
Apr 122026
Mar 23

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.

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 Cohagen, MT.

Soil in Cohagen, MT

The soil mapped at the center of ZIP 59322 is Kobase — silty clay loam, well drained.

TextureSilty clay loamholds water and nutrients; slow to drain and warm up

pH7.5slightly alkaline; most vegetables like 6.0–7.0

DrainageWell drainednatural drainage class

Organic matter1.5%low — add compost

Hydrologic groupCwater soaks in slowly

Farmland classFarmland of statewide importanceUSDA classification

Map unit: Kobase-Sonnett, thin surface, silty clay loams, 2 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 59322; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Cohagen, MT

Summer high86 °Faverage high, July

Winter low7 °Faverage low, January

Hot days32days a year at 90 °F or more

Freezing nights185nights a year at 32 °F or less

Growing degree days2,046base 50 °F — the season’s usable heat

Longest day15 h 54 mindaylight on June 21

Shortest day8 h 30 mindaylight on December 21

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

Precipitation12.3 inper year, rain and melted snow

Snowfall25 inper year; 53 days with snow on the ground

Average high and low, by month

Precipitation by month inches · ❄ = snowfall

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Cohagen, MT (4 mi away); precipitation: Cohagen, MT (4 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

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

Montana planting zones →

Questions about 59322

What planting zone is ZIP code 59322?

ZIP code 59322 (Cohagen, 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 Cohagen, MT?

The median last spring frost (32 °F) near 59322 is May 25; after June 9 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Cohagen station.

When is the first frost in Cohagen, MT?

The median first fall frost near 59322 is September 14, giving a median frost-free growing season of 110 days.

When should I plant tomatoes in 59322?

Start tomato seeds indoors around Mar 30 – Apr 13 and set transplants outside around Jun 1 – Jun 15, one to three weeks after the median last frost.

How much rain and snow does 59322 get?

About 12.3 inches of precipitation a year and 25 inches of snowfall (NOAA 1991–2020 normals, Cohagen station).

How hot do summers get in Cohagen, MT?

The average high peaks at 86 °F in July, with about 32 days a year at 90 °F or more.

What kind of soil does 59322 have?

The USDA soil survey maps Kobase at the center of ZIP 59322: silty clay loam, well drained, pH about 7.5 (slightly alkaline).

Did spring come early in Cohagen, MT in 2026?

Spring leaf-out near 59322 came on Mar 23 in 2026, 20 days earlier than the 1991–2020 average (Apr 12), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Cohagen, MT?

Long-day onions: the longest day near 59322 is 15 h 54 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).

Did the zone for 59322 change?

Yes. The 2012 USDA map put 59322 in zone 3b; the 2023 map puts it in zone 4a. The newer map uses 1991–2020 data and more weather stations.