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

Planting zone for 59422 — Choteau, MT

ZIP code 59422 (Choteau, Teton County) is in USDA zone 4b: the coldest winter night averages −25 to −20 °F. The median last spring frost is May 16 and the first fall frost September 27.

Where ZIP 59422 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 16

First frostSep 27

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 Choteau, 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 Choteau, MT

JanFebMarAprMayJunJulAugSepOctNovDec

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

Last spring frostMay 16median — 50% chance of a later frost

Safe for tender plantsMay 28only 10% chance of frost after

First fall frostSeptember 27median — 10% chance by Sep 16

Growing season133 daysfrost-free, median

A hard freeze (28 °F) usually ends around May 2 and returns around October 6.

From the NOAA station Bynum 4 Sse, MT — 11 miles away, elevation 4,039 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 59422

JanFebMarAprMayJunJulAugSepOctNovDec

PeasSow outdoors · Apr 4 – Apr 18

SpinachSow outdoors · Apr 4 – Apr 25

Broccoli, cabbageStart indoors · Mar 7 – Mar 21

Broccoli, cabbageTransplant · Apr 25 – May 9

Onion setsPlant outdoors · Apr 18 – May 2

PotatoesPlant outdoors · Apr 25 – May 9

LettuceSow outdoors · Apr 18 – May 2

Carrots, beetsSow outdoors · Apr 25 – May 9

TomatoesStart indoors · Mar 21 – Apr 4

TomatoesTransplant · May 23 – Jun 6

Peppers, eggplantStart indoors · Mar 7 – Mar 21

Peppers, eggplantTransplant · May 30 – Jun 13

BeansSow outdoors · May 23 – Jun 6

Sweet cornSow outdoors · May 23 – Jun 6

Cucumbers, squashSow outdoors · May 23 – Jun 6

Fall lettuce, spinachSow outdoors · Aug 2 – Aug 16

GarlicPlant cloves · Sep 13 – Oct 18

Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (May 16) and first fall frost (Sep 27) 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 59422 came on Mar 22 — 31 days earlier than the 1991–2020 average (Apr 22).

average
Apr 222026
Mar 22

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 4b in Montana

506 plants native to the lower 48 states, recorded in Montana, and rated by the USDA to survive −25 °F or colder — the bottom of zone 4b. 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 Choteau, MT.

Soil in Choteau, MT

The soil mapped at the center of ZIP 59422 is Windham — gravelly loam, well drained.

TextureGravelly loama good balance for most vegetables

pH7.9alkaline; most vegetables like 6.0–7.0

DrainageWell drainednatural drainage class

Organic matter3%moderate

Hydrologic groupBwater soaks in moderately

Farmland classNot prime farmlandUSDA classification

Map unit: Windham gravelly 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 59422; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Choteau, MT

Summer high80 °Faverage high, July

Winter low14 °Faverage low, January

Hot days9days a year at 90 °F or more

Freezing nights169nights a year at 32 °F or less

Growing degree days1,679base 50 °F — the season’s usable heat

Longest day16 h 01 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)

Precipitation15.3 inper year, rain and melted snow

Average high and low, by month

Precipitation by month inches

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Bynum 4 Sse, MT (11 mi away); precipitation: Bynum 4 Sse, MT (11 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

All 8 nearest ZIP codes share zone 4b.

Fairfield, MT · 23 mi

594104b

Augusta, MT · 24 mi

594484b

Heart Butte, MT · 34 mi

594864b

Valier, MT · 35 mi

594434b

Fort Shaw, MT · 36 mi

Montana planting zones →

Questions about 59422

What planting zone is ZIP code 59422?

ZIP code 59422 (Choteau, 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 Choteau, MT?

The median last spring frost (32 °F) near 59422 is May 16; after May 28 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Bynum 4 Sse station.

When is the first frost in Choteau, MT?

The median first fall frost near 59422 is September 27, giving a median frost-free growing season of 133 days.

When should I plant tomatoes in 59422?

Start tomato seeds indoors around Mar 21 – Apr 4 and set transplants outside around May 23 – Jun 6, one to three weeks after the median last frost.

How much rain and snow does 59422 get?

About 15.3 inches of precipitation a year (NOAA 1991–2020 normals, Bynum 4 Sse station).

How hot do summers get in Choteau, MT?

The average high peaks at 80 °F in July, with about 9 days a year at 90 °F or more.

What kind of soil does 59422 have?

The USDA soil survey maps Windham at the center of ZIP 59422: gravelly loam, well drained, pH about 7.9 (alkaline).

Did spring come early in Choteau, MT in 2026?

Spring leaf-out near 59422 came on Mar 22 in 2026, 31 days earlier than the 1991–2020 average (Apr 22), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Choteau, MT?

Long-day onions: the longest day near 59422 is 16 h 01 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).

Did the zone for 59422 change?

Yes. The 2012 USDA map put 59422 in zone 4a; the 2023 map puts it in zone 4b. The newer map uses 1991–2020 data and more weather stations.