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

Planting zone for 59457 — Lewistown, MT

ZIP code 59457 (Lewistown, Fergus County) is in USDA zone 4b: the coldest winter night averages −25 to −20 °F. The median last spring frost is May 14 and the first fall frost September 28.

Where ZIP 59457 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 14

First frostSep 28

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 Lewistown, 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 Lewistown, MT

JanFebMarAprMayJunJulAugSepOctNovDec

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

Last spring frostMay 14median — 50% chance of a later frost

Safe for tender plantsMay 27only 10% chance of frost after

First fall frostSeptember 28median — 10% chance by Sep 14

Growing season135 daysfrost-free, median

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

From the NOAA station Lewistown, MT — 7 miles away, elevation 3,911 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 59457

JanFebMarAprMayJunJulAugSepOctNovDec

PeasSow outdoors · Apr 2 – Apr 16

SpinachSow outdoors · Apr 2 – Apr 23

Broccoli, cabbageStart indoors · Mar 5 – Mar 19

Broccoli, cabbageTransplant · Apr 23 – May 7

Onion setsPlant outdoors · Apr 16 – Apr 30

PotatoesPlant outdoors · Apr 23 – May 7

LettuceSow outdoors · Apr 16 – Apr 30

Carrots, beetsSow outdoors · Apr 23 – May 7

TomatoesStart indoors · Mar 19 – Apr 2

TomatoesTransplant · May 21 – Jun 4

Peppers, eggplantStart indoors · Mar 5 – Mar 19

Peppers, eggplantTransplant · May 28 – Jun 11

BeansSow outdoors · May 21 – Jun 4

Sweet cornSow outdoors · May 21 – Jun 4

Cucumbers, squashSow outdoors · May 21 – Jun 4

Fall lettuce, spinachSow outdoors · Aug 3 – Aug 17

GarlicPlant cloves · Sep 14 – Oct 19

Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (May 14) and first fall frost (Sep 28) 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 59457 came on Apr 6 — 16 days earlier than the 1991–2020 average (Apr 22).

average
Apr 222026
Apr 6

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 Lewistown, MT.

Soil in Lewistown, MT

The soil mapped at the center of ZIP 59457 is Hughesville — very flaggy clay loam, well drained.

TextureVery flaggy clay loamholds water and nutrients; slow to drain and warm up

pH7.2neutral; most vegetables like 6.0–7.0

DrainageWell drainednatural drainage class

Organic matter3%moderate

Hydrologic groupCwater soaks in slowly

Farmland classNot prime farmlandUSDA classification

Map unit: Widen-Hughesville-Lipke complex, 15 to 60 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 59457; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Lewistown, MT

Summer high87 °Faverage high, July

Winter low15 °Faverage low, January

Hot days24days a year at 90 °F or more

Freezing nights166nights a year at 32 °F or less

Growing degree days2,142base 50 °F — the season’s usable heat

Longest day15 h 55 mindaylight on June 21

Shortest day8 h 29 mindaylight on December 21

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

Precipitation17.2 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: Lewistown, MT (7 mi away); precipitation: Lewistown Municipal Airport, MT (9 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

All 8 nearest ZIP codes share zone 4b.

594514b

Hilger, MT · 18 mi

594414b

Forest Grove, MT · 24 mi

Montana planting zones →

Questions about 59457

What planting zone is ZIP code 59457?

ZIP code 59457 (Lewistown, 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 Lewistown, MT?

The median last spring frost (32 °F) near 59457 is May 14; after May 27 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Lewistown station.

When is the first frost in Lewistown, MT?

The median first fall frost near 59457 is September 28, giving a median frost-free growing season of 135 days.

When should I plant tomatoes in 59457?

Start tomato seeds indoors around Mar 19 – Apr 2 and set transplants outside around May 21 – Jun 4, one to three weeks after the median last frost.

How much rain and snow does 59457 get?

About 17.2 inches of precipitation a year (NOAA 1991–2020 normals, Lewistown Municipal Airport station).

How hot do summers get in Lewistown, MT?

The average high peaks at 87 °F in July, with about 24 days a year at 90 °F or more.

What kind of soil does 59457 have?

The USDA soil survey maps Hughesville at the center of ZIP 59457: very flaggy clay loam, well drained, pH about 7.2 (neutral).

Did spring come early in Lewistown, MT in 2026?

Spring leaf-out near 59457 came on Apr 6 in 2026, 16 days earlier than the 1991–2020 average (Apr 22), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Lewistown, MT?

Long-day onions: the longest day near 59457 is 15 h 55 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).

Did the zone for 59457 change?

Yes. The 2012 USDA map put 59457 in zone 4a; the 2023 map puts it in zone 4b. The newer map uses 1991–2020 data and more weather stations.