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

Planting zone for 59230 — Glasgow, MT

ZIP code 59230 (Glasgow, Valley County) is in USDA zone 4a: the coldest winter night averages −30 to −25 °F. The median last spring frost is May 3 and the first fall frost October 1.

Where ZIP 59230 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 3

First frostOct 1

2012 zone4a

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 4a means →

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for Glasgow, 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 Glasgow, MT

JanFebMarAprMayJunJulAugSepOctNovDec

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

Last spring frostMay 3median — 50% chance of a later frost

Safe for tender plantsMay 15only 10% chance of frost after

First fall frostOctober 1median — 10% chance by Sep 19

Growing season151 daysfrost-free, median

A hard freeze (28 °F) usually ends around April 23 and returns around October 11.

From the NOAA station Glasgow #2, MT — 9 miles away, elevation 2,090 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 59230

JanFebMarAprMayJunJulAugSepOctNovDec

PeasSow outdoors · Mar 22 – Apr 5

SpinachSow outdoors · Mar 22 – Apr 12

Broccoli, cabbageStart indoors · Feb 22 – Mar 8

Broccoli, cabbageTransplant · Apr 12 – Apr 26

Onion setsPlant outdoors · Apr 5 – Apr 19

PotatoesPlant outdoors · Apr 12 – Apr 26

LettuceSow outdoors · Apr 5 – Apr 19

Carrots, beetsSow outdoors · Apr 12 – Apr 26

TomatoesStart indoors · Mar 8 – Mar 22

TomatoesTransplant · May 10 – May 24

Peppers, eggplantStart indoors · Feb 22 – Mar 8

Peppers, eggplantTransplant · May 17 – May 31

BeansSow outdoors · May 10 – May 24

Sweet cornSow outdoors · May 10 – May 24

Cucumbers, squashSow outdoors · May 10 – May 24

Fall lettuce, spinachSow outdoors · Aug 6 – Aug 20

GarlicPlant cloves · Sep 17 – Oct 22

Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (May 3) and first fall frost (Oct 1) 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 59230 came on Apr 8 — 8 days earlier than the 1991–2020 average (Apr 16).

average
Apr 162026
Apr 8

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 Glasgow, MT.

Soil in Glasgow, MT

The soil mapped at the center of ZIP 59230 is Elloam — loam, well drained.

TextureLoama good balance for most vegetables

pH6.7neutral; most vegetables like 6.0–7.0

DrainageWell drainednatural drainage class

Organic matter1.5%low — add compost

Hydrologic groupDwater soaks in very slowly

Farmland classNot prime farmlandUSDA classification

Map unit: Elloam-Absher complex, 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 59230; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Glasgow, MT

Summer high87 °Faverage high, July

Winter low4 °Faverage low, January

Hot days33days a year at 90 °F or more

Freezing nights175nights a year at 32 °F or less

Growing degree days2,492base 50 °F — the season’s usable heat

Longest day16 h 04 mindaylight on June 21

Shortest day8 h 21 mindaylight on December 21

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

Precipitation13.4 inper year, rain and melted snow

Snowfall44 inper year; 81 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: Glasgow #2, MT (9 mi away); precipitation: Glasgow WFO, MT (9 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

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

592734a

Vandalia, MT · 14 mi

592314a

Saint Marie, MT · 22 mi

Fort Peck, MT · 31 mi

Montana planting zones →

Questions about 59230

What planting zone is ZIP code 59230?

ZIP code 59230 (Glasgow, 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 Glasgow, MT?

The median last spring frost (32 °F) near 59230 is May 3; after May 15 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Glasgow #2 station.

When is the first frost in Glasgow, MT?

The median first fall frost near 59230 is October 1, giving a median frost-free growing season of 151 days.

When should I plant tomatoes in 59230?

Start tomato seeds indoors around Mar 8 – Mar 22 and set transplants outside around May 10 – May 24, one to three weeks after the median last frost.

How much rain and snow does 59230 get?

About 13.4 inches of precipitation a year and 44 inches of snowfall (NOAA 1991–2020 normals, Glasgow WFO station).

How hot do summers get in Glasgow, MT?

The average high peaks at 87 °F in July, with about 33 days a year at 90 °F or more.

What kind of soil does 59230 have?

The USDA soil survey maps Elloam at the center of ZIP 59230: loam, well drained, pH about 6.7 (neutral).

Did spring come early in Glasgow, MT in 2026?

Spring leaf-out near 59230 came on Apr 8 in 2026, 8 days earlier than the 1991–2020 average (Apr 16), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Glasgow, MT?

Long-day onions: the longest day near 59230 is 16 h 04 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).