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

Planting zone for 59463 — Monarch, MT

ZIP code 59463 (Monarch, Cascade County) is in USDA zone 4b: the coldest winter night averages −25 to −20 °F. The median last spring frost is June 6 and the first fall frost September 12.

Where ZIP 59463 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 6

First frostSep 12

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 Monarch, 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 Monarch, MT

JanFebMarAprMayJunJulAugSepOctNovDec

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

Last spring frostJune 6median — 50% chance of a later frost

Safe for tender plantsJune 28only 10% chance of frost after

First fall frostSeptember 12median — 10% chance by Aug 29

Growing season99 daysfrost-free, median

A hard freeze (28 °F) usually ends around May 18 and returns around September 26.

From the NOAA station Neihart 8 Nnw, MT — 4 miles away, elevation 5,230 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 59463

JanFebMarAprMayJunJulAugSepOctNovDec

PeasSow outdoors · Apr 25 – May 9

SpinachSow outdoors · Apr 25 – May 16

Broccoli, cabbageStart indoors · Mar 28 – Apr 11

Broccoli, cabbageTransplant · May 16 – May 30

Onion setsPlant outdoors · May 9 – May 23

PotatoesPlant outdoors · May 16 – May 30

LettuceSow outdoors · May 9 – May 23

Carrots, beetsSow outdoors · May 16 – May 30

TomatoesStart indoors · Apr 11 – Apr 25

TomatoesTransplant · Jun 13 – Jun 27

Peppers, eggplantStart indoors · Mar 28 – Apr 11

Peppers, eggplantTransplant · Jun 20 – Jul 4

BeansSow outdoors · Jun 13 – Jun 27

Sweet cornSow outdoors · Jun 13 – Jun 27

Cucumbers, squashSow outdoors · Jun 13 – Jun 27

Fall lettuce, spinachSow outdoors · Jul 18 – Aug 1

GarlicPlant cloves · Aug 29 – Oct 3

Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (Jun 6) and first fall frost (Sep 12) 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 59463 came on May 7 — 3 days earlier than the 1991–2020 average (May 10).

average
May 102026
May 7

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).

Soil in Monarch, MT

The soil mapped at the center of ZIP 59463 is Lake Creek — slightly decomposed plant material, well drained.

TextureSlightly decomposed plant materialtop layer

pH5.5moderately acidic; most vegetables like 6.0–7.0

DrainageWell drainednatural drainage class

Organic matter75%high

Hydrologic groupCwater soaks in slowly

Farmland classNot prime farmlandUSDA classification

Map unit: Lake Creek, very stony-Findon-Redfern, extremely stony famiies, complex, 35 to 70 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 59463; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Monarch, MT

Summer high81 °Faverage high, July

Winter low16 °Faverage low, January

Hot days8days a year at 90 °F or more

Freezing nights196nights a year at 32 °F or less

Growing degree days1,469base 50 °F — the season’s usable heat

Longest day15 h 54 mindaylight on June 21

Shortest day8 h 30 mindaylight on December 21

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

Precipitation30.7 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: Neihart 8 Nnw, MT (4 mi away); precipitation: Stringer Creek, MT (8 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

All 8 nearest ZIP codes share zone 4b.

594654b

Neihart, MT · 11 mi

594694b

Raynesford, MT · 13 mi

Sand Coulee, MT · 26 mi

594054b

Great Falls, MT · 26 mi

594794b

Stanford, MT · 26 mi

Montana planting zones →

Questions about 59463

What planting zone is ZIP code 59463?

ZIP code 59463 (Monarch, 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 Monarch, MT?

The median last spring frost (32 °F) near 59463 is June 6; after June 28 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Neihart 8 Nnw station.

When is the first frost in Monarch, MT?

The median first fall frost near 59463 is September 12, giving a median frost-free growing season of 99 days.

When should I plant tomatoes in 59463?

Start tomato seeds indoors around Apr 11 – Apr 25 and set transplants outside around Jun 13 – Jun 27, one to three weeks after the median last frost.

How much rain and snow does 59463 get?

About 30.7 inches of precipitation a year (NOAA 1991–2020 normals, Stringer Creek station).

How hot do summers get in Monarch, MT?

The average high peaks at 81 °F in July, with about 8 days a year at 90 °F or more.

What kind of soil does 59463 have?

The USDA soil survey maps Lake Creek at the center of ZIP 59463: slightly decomposed plant material, well drained, pH about 5.5 (moderately acidic).

Did spring come early in Monarch, MT in 2026?

Spring leaf-out near 59463 came on May 7 in 2026, 3 days earlier than the 1991–2020 average (May 10), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Monarch, MT?

Long-day onions: the longest day near 59463 is 15 h 54 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).

Did the zone for 59463 change?

Yes. The 2012 USDA map put 59463 in zone 4a; the 2023 map puts it in zone 4b. The newer map uses 1991–2020 data and more weather stations.