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

Planting zone for 59039 — Ingomar, MT

ZIP code 59039 (Ingomar, Rosebud County) is in USDA zone 4b: the coldest winter night averages −25 to −20 °F. The median last spring frost is May 21 and the first fall frost September 19.

Where ZIP 59039 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 21

First frostSep 19

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 Ingomar, 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 Ingomar, MT

JanFebMarAprMayJunJulAugSepOctNovDec

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

Last spring frostMay 21median — 50% chance of a later frost

Safe for tender plantsJune 4only 10% chance of frost after

First fall frostSeptember 19median — 10% chance by Sep 6

Growing season120 daysfrost-free, median

A hard freeze (28 °F) usually ends around May 10 and returns around September 28.

From the NOAA station Ingomar 9 E, 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 59039

JanFebMarAprMayJunJulAugSepOctNovDec

PeasSow outdoors · Apr 9 – Apr 23

SpinachSow outdoors · Apr 9 – Apr 30

Broccoli, cabbageStart indoors · Mar 12 – Mar 26

Broccoli, cabbageTransplant · Apr 30 – May 14

Onion setsPlant outdoors · Apr 23 – May 7

PotatoesPlant outdoors · Apr 30 – May 14

LettuceSow outdoors · Apr 23 – May 7

Carrots, beetsSow outdoors · Apr 30 – May 14

TomatoesStart indoors · Mar 26 – Apr 9

TomatoesTransplant · May 28 – Jun 11

Peppers, eggplantStart indoors · Mar 12 – Mar 26

Peppers, eggplantTransplant · Jun 4 – Jun 18

BeansSow outdoors · May 28 – Jun 11

Sweet cornSow outdoors · May 28 – Jun 11

Cucumbers, squashSow outdoors · May 28 – Jun 11

Fall lettuce, spinachSow outdoors · Jul 25 – Aug 8

GarlicPlant cloves · Sep 5 – Oct 10

Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (May 21) and first fall frost (Sep 19) 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 59039 came on Mar 23 — 17 days earlier than the 1991–2020 average (Apr 9).

average
Apr 92026
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 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 Ingomar, MT.

Soil in Ingomar, MT

The soil mapped at the center of ZIP 59039 is Brunelda — silty clay, well drained.

TextureSilty clayholds water and nutrients; slow to drain and warm up

pH7.9alkaline; most vegetables like 6.0–7.0

DrainageWell drainednatural drainage class

Organic matter2%moderate

Hydrologic groupCwater soaks in slowly

Farmland classNot prime farmlandUSDA classification

Map unit: Brunelda-Vaeda-Nobe complex, 1 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 59039; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Ingomar, MT

Summer high88 °Faverage high, July

Winter low4 °Faverage low, January

Hot days38days a year at 90 °F or more

Freezing nights187nights a year at 32 °F or less

Growing degree days2,213base 50 °F — the season’s usable heat

Longest day15 h 51 mindaylight on June 21

Shortest day8 h 33 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

Snowfall30 inper year; 63 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: Ingomar 9 E, MT (9 mi away); precipitation: Ingomar 9 E, 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.

Musselshell, MT · 39 mi

Montana planting zones →

Questions about 59039

What planting zone is ZIP code 59039?

ZIP code 59039 (Ingomar, 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 Ingomar, MT?

The median last spring frost (32 °F) near 59039 is May 21; after June 4 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Ingomar 9 E station.

When is the first frost in Ingomar, MT?

The median first fall frost near 59039 is September 19, giving a median frost-free growing season of 120 days.

When should I plant tomatoes in 59039?

Start tomato seeds indoors around Mar 26 – Apr 9 and set transplants outside around May 28 – Jun 11, one to three weeks after the median last frost.

How much rain and snow does 59039 get?

About 13.6 inches of precipitation a year and 30 inches of snowfall (NOAA 1991–2020 normals, Ingomar 9 E station).

How hot do summers get in Ingomar, MT?

The average high peaks at 88 °F in July, with about 38 days a year at 90 °F or more.

What kind of soil does 59039 have?

The USDA soil survey maps Brunelda at the center of ZIP 59039: silty clay, well drained, pH about 7.9 (alkaline).

Did spring come early in Ingomar, MT in 2026?

Spring leaf-out near 59039 came on Mar 23 in 2026, 17 days earlier than the 1991–2020 average (Apr 9), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Ingomar, MT?

Long-day onions: the longest day near 59039 is 15 h 51 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).

Did the zone for 59039 change?

Yes. The 2012 USDA map put 59039 in zone 4a; the 2023 map puts it in zone 4b. The newer map uses 1991–2020 data and more weather stations.