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

Planting zone for 59450 — Highwood, MT

ZIP code 59450 (Highwood, Chouteau County) is in USDA zone 4b: the coldest winter night averages −25 to −20 °F. The median last spring frost is May 7 and the first fall frost October 2.

Where ZIP 59450 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 7

First frostOct 2

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 Highwood, 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 Highwood, MT

JanFebMarAprMayJunJulAugSepOctNovDec

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

Last spring frostMay 7median — 50% chance of a later frost

Safe for tender plantsMay 21only 10% chance of frost after

First fall frostOctober 2median — 10% chance by Sep 19

Growing season149 daysfrost-free, median

A hard freeze (28 °F) usually ends around April 24 and returns around October 15.

From the NOAA station Highwood 7 Ne, MT — 7 miles away, elevation 3,599 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 59450

JanFebMarAprMayJunJulAugSepOctNovDec

PeasSow outdoors · Mar 26 – Apr 9

SpinachSow outdoors · Mar 26 – Apr 16

Broccoli, cabbageStart indoors · Feb 26 – Mar 12

Broccoli, cabbageTransplant · Apr 16 – Apr 30

Onion setsPlant outdoors · Apr 9 – Apr 23

PotatoesPlant outdoors · Apr 16 – Apr 30

LettuceSow outdoors · Apr 9 – Apr 23

Carrots, beetsSow outdoors · Apr 16 – Apr 30

TomatoesStart indoors · Mar 12 – Mar 26

TomatoesTransplant · May 14 – May 28

Peppers, eggplantStart indoors · Feb 26 – Mar 12

Peppers, eggplantTransplant · May 21 – Jun 4

BeansSow outdoors · May 14 – May 28

Sweet cornSow outdoors · May 14 – May 28

Cucumbers, squashSow outdoors · May 14 – May 28

Fall lettuce, spinachSow outdoors · Aug 7 – Aug 21

GarlicPlant cloves · Sep 18 – Oct 23

Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (May 7) and first fall frost (Oct 2) 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 59450 came on Mar 5 — 36 days earlier than the 1991–2020 average (Apr 10).

average
Apr 102026
Mar 5

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 Highwood, MT.

Soil in Highwood, MT

The soil mapped at the center of ZIP 59450 is Sweetgrass — clay loam, well drained.

TextureClay loamholds water and nutrients; slow to drain and warm up

pH7.2neutral; most vegetables like 6.0–7.0

DrainageWell drainednatural drainage class

Organic matter4%moderate

Hydrologic groupCwater soaks in slowly

Farmland classNot prime farmlandUSDA classification

Map unit: Sweetgrass-Beaverton complex, 0 to 2 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 59450; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Highwood, MT

Summer high85 °Faverage high, July

Winter low17 °Faverage low, January

Hot days24days a year at 90 °F or more

Freezing nights141nights a year at 32 °F or less

Growing degree days2,245base 50 °F — the season’s usable heat

Longest day15 h 59 mindaylight on June 21

Shortest day8 h 26 mindaylight on December 21

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

Precipitation15.1 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: Highwood 7 Ne, MT (7 mi away); precipitation: Highwood 7 Ne, MT (7 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.

Great Falls, MT · 24 mi

594694b

Raynesford, MT · 25 mi

594204a

Carter, MT · 26 mi

594724b

Sand Coulee, MT · 26 mi

594424a

Fort Benton, MT · 26 mi

Montana planting zones →

Questions about 59450

What planting zone is ZIP code 59450?

ZIP code 59450 (Highwood, 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 Highwood, MT?

The median last spring frost (32 °F) near 59450 is May 7; after May 21 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Highwood 7 Ne station.

When is the first frost in Highwood, MT?

The median first fall frost near 59450 is October 2, giving a median frost-free growing season of 149 days.

When should I plant tomatoes in 59450?

Start tomato seeds indoors around Mar 12 – Mar 26 and set transplants outside around May 14 – May 28, one to three weeks after the median last frost.

How much rain and snow does 59450 get?

About 15.1 inches of precipitation a year (NOAA 1991–2020 normals, Highwood 7 Ne station).

How hot do summers get in Highwood, MT?

The average high peaks at 85 °F in July, with about 24 days a year at 90 °F or more.

What kind of soil does 59450 have?

The USDA soil survey maps Sweetgrass at the center of ZIP 59450: clay loam, well drained, pH about 7.2 (neutral).

Did spring come early in Highwood, MT in 2026?

Spring leaf-out near 59450 came on Mar 5 in 2026, 36 days earlier than the 1991–2020 average (Apr 10), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Highwood, MT?

Long-day onions: the longest day near 59450 is 15 h 59 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).

Did the zone for 59450 change?

Yes. The 2012 USDA map put 59450 in zone 4a; the 2023 map puts it in zone 4b. The newer map uses 1991–2020 data and more weather stations.