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

Planting zone for 59531 — Joplin, MT

ZIP code 59531 (Joplin, Liberty County) is in USDA zone 4a: the coldest winter night averages −30 to −25 °F. The median last spring frost is May 30 and the first fall frost September 11.

Where ZIP 59531 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 30

First frostSep 11

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 Joplin, 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 Joplin, MT

JanFebMarAprMayJunJulAugSepOctNovDec

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

Last spring frostMay 30median — 50% chance of a later frost

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

First fall frostSeptember 11median — 10% chance by Aug 27

Growing season103 daysfrost-free, median

A hard freeze (28 °F) usually ends around May 16 and returns around September 23.

From the NOAA station Rudyard 21 N, MT — 11 miles away, elevation 2,999 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 59531

JanFebMarAprMayJunJulAugSepOctNovDec

PeasSow outdoors · Apr 18 – May 2

SpinachSow outdoors · Apr 18 – May 9

Broccoli, cabbageStart indoors · Mar 21 – Apr 4

Broccoli, cabbageTransplant · May 9 – May 23

Onion setsPlant outdoors · May 2 – May 16

PotatoesPlant outdoors · May 9 – May 23

LettuceSow outdoors · May 2 – May 16

Carrots, beetsSow outdoors · May 9 – May 23

TomatoesStart indoors · Apr 4 – Apr 18

TomatoesTransplant · Jun 6 – Jun 20

Peppers, eggplantStart indoors · Mar 21 – Apr 4

Peppers, eggplantTransplant · Jun 13 – Jun 27

BeansSow outdoors · Jun 6 – Jun 20

Sweet cornSow outdoors · Jun 6 – Jun 20

Cucumbers, squashSow outdoors · Jun 6 – Jun 20

Fall lettuce, spinachSow outdoors · Jul 17 – Jul 31

GarlicPlant cloves · Aug 28 – Oct 2

Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (May 30) and first fall frost (Sep 11) 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 59531 came on Mar 29 — 19 days earlier than the 1991–2020 average (Apr 17).

average
Apr 172026
Mar 29

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 Joplin, MT.

Soil in Joplin, MT

The soil mapped at the center of ZIP 59531 is Joplin — loam, well drained.

TextureLoama good balance for most vegetables

pH7.1neutral; most vegetables like 6.0–7.0

DrainageWell drainednatural drainage class

Organic matter2%moderate

Hydrologic groupCwater soaks in slowly

Farmland classFarmland of statewide importanceUSDA classification

Map unit: Joplin-Hillon loams, 2 to 8 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 59531; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Joplin, MT

Summer high83 °Faverage high, July

Winter low5 °Faverage low, January

Hot days22days a year at 90 °F or more

Freezing nights202nights a year at 32 °F or less

Growing degree days1,574base 50 °F — the season’s usable heat

Longest day16 h 10 mindaylight on June 21

Shortest day8 h 15 mindaylight on December 21

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

Precipitation11.3 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: Rudyard 21 N, MT (11 mi away); precipitation: Rudyard 21 N, MT (11 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.

595304a

Inverness, MT · 13 mi

Montana planting zones →

Questions about 59531

What planting zone is ZIP code 59531?

ZIP code 59531 (Joplin, 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 Joplin, MT?

The median last spring frost (32 °F) near 59531 is May 30; after June 15 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Rudyard 21 N station.

When is the first frost in Joplin, MT?

The median first fall frost near 59531 is September 11, giving a median frost-free growing season of 103 days.

When should I plant tomatoes in 59531?

Start tomato seeds indoors around Apr 4 – Apr 18 and set transplants outside around Jun 6 – Jun 20, one to three weeks after the median last frost.

How much rain and snow does 59531 get?

About 11.3 inches of precipitation a year (NOAA 1991–2020 normals, Rudyard 21 N station).

How hot do summers get in Joplin, MT?

The average high peaks at 83 °F in July, with about 22 days a year at 90 °F or more.

What kind of soil does 59531 have?

The USDA soil survey maps Joplin at the center of ZIP 59531: loam, well drained, pH about 7.1 (neutral).

Did spring come early in Joplin, MT in 2026?

Spring leaf-out near 59531 came on Mar 29 in 2026, 19 days earlier than the 1991–2020 average (Apr 17), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Joplin, MT?

Long-day onions: the longest day near 59531 is 16 h 10 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).