Data: 2023 USDA zones (PRISM/OSU) · NOAA 1991–2020 normals · updated Oct 30, 2026

Planting zone for 59477 — Simms, MT

ZIP code 59477 (Simms, Cascade County) is in USDA zone 4b: the coldest winter night averages −25 to −20 °F. The median last spring frost is June 2 and the first fall frost September 10.

Where ZIP 59477 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 frostJun 2

First frostSep 10

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 Simms, 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 Simms, MT

JanFebMarAprMayJunJulAugSepOctNovDec

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

Last spring frostJune 2median — 50% chance of a later frost

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

First fall frostSeptember 10median — 10% chance by Aug 25

Growing season96 daysfrost-free, median

A hard freeze (28 °F) usually ends around May 18 and returns around September 22.

From the NOAA station Sun Rvr 4 S, MT — 11 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 59477

JanFebMarAprMayJunJulAugSepOctNovDec

PeasSow outdoors · Apr 21 – May 5

SpinachSow outdoors · Apr 21 – May 12

Broccoli, cabbageStart indoors · Mar 24 – Apr 7

Broccoli, cabbageTransplant · May 12 – May 26

Onion setsPlant outdoors · May 5 – May 19

PotatoesPlant outdoors · May 12 – May 26

LettuceSow outdoors · May 5 – May 19

Carrots, beetsSow outdoors · May 12 – May 26

TomatoesStart indoors · Apr 7 – Apr 21

TomatoesTransplant · Jun 9 – Jun 23

Peppers, eggplantStart indoors · Mar 24 – Apr 7

Peppers, eggplantTransplant · Jun 16 – Jun 30

BeansSow outdoors · Jun 9 – Jun 23

Sweet cornSow outdoors · Jun 9 – Jun 23

Cucumbers, squashSow outdoors · Jun 9 – Jun 23

Fall lettuce, spinachSow outdoors · Jul 16 – Jul 30

GarlicPlant cloves · Aug 27 – Oct 1

Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (Jun 2) and first fall frost (Sep 10) 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 59477 came on Mar 12 — 29 days earlier than the 1991–2020 average (Apr 10).

average
Apr 102026
Mar 12

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 Simms, MT.

Soil in Simms, MT

The soil mapped at the center of ZIP 59477 is Reeder — loam, well drained.

TextureLoama good balance for most vegetables

pH7.0neutral; 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: Reeder loam, 8 to 25 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 59477; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Simms, MT

Summer high83 °Faverage high, July

Winter low13 °Faverage low, January

Hot days18days a year at 90 °F or more

Freezing nights170nights a year at 32 °F or less

Growing degree days1,586base 50 °F — the season’s usable heat

Longest day15 h 58 mindaylight on June 21

Shortest day8 h 27 mindaylight on December 21

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

Precipitation12.3 inper year, rain and melted snow

Snowfall46 inper year; 55 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: Sun Rvr 4 S, MT (11 mi away); precipitation: Simms 1 Ne, MT (4 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

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

594434b

Fort Shaw, MT · 11 mi

594834a

Sun River, MT · 11 mi

594364b

Fairfield, MT · 14 mi

Wolf Creek, MT · 26 mi

594214b

Cascade, MT · 29 mi

Montana planting zones →

Questions about 59477

What planting zone is ZIP code 59477?

ZIP code 59477 (Simms, 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 Simms, MT?

The median last spring frost (32 °F) near 59477 is June 2; after June 21 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Sun Rvr 4 S station.

When is the first frost in Simms, MT?

The median first fall frost near 59477 is September 10, giving a median frost-free growing season of 96 days.

When should I plant tomatoes in 59477?

Start tomato seeds indoors around Apr 7 – Apr 21 and set transplants outside around Jun 9 – Jun 23, one to three weeks after the median last frost.

How much rain and snow does 59477 get?

About 12.3 inches of precipitation a year and 46 inches of snowfall (NOAA 1991–2020 normals, Simms 1 Ne station).

How hot do summers get in Simms, MT?

The average high peaks at 83 °F in July, with about 18 days a year at 90 °F or more.

What kind of soil does 59477 have?

The USDA soil survey maps Reeder at the center of ZIP 59477: loam, well drained, pH about 7.0 (neutral).

Did spring come early in Simms, MT in 2026?

Spring leaf-out near 59477 came on Mar 12 in 2026, 29 days earlier than the 1991–2020 average (Apr 10), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Simms, MT?

Long-day onions: the longest day near 59477 is 15 h 58 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).

Did the zone for 59477 change?

Yes. The 2012 USDA map put 59477 in zone 4a; the 2023 map puts it in zone 4b. The newer map uses 1991–2020 data and more weather stations.