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

Planting zone for 59041 — Joliet, MT

ZIP code 59041 (Joliet, Carbon County) is in USDA zone 5a: the coldest winter night averages −20 to −15 °F. The median last spring frost is May 29 and the first fall frost September 15.

Where ZIP 59041 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.

Zone5a−20 to −15 °F

Coldest night−28.9 to −26.1 °C

Last frostMay 29

First frostSep 15

2012 zone4b

Was 4b 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 5a means →

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for Joliet, 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 Joliet, MT

JanFebMarAprMayJunJulAugSepOctNovDec

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

Last spring frostMay 29median — 50% chance of a later frost

Safe for tender plantsJune 17only 10% chance of frost after

First fall frostSeptember 15median — 10% chance by Sep 1

Growing season107 daysfrost-free, median

A hard freeze (28 °F) usually ends around May 13 and returns around September 26.

From the NOAA station Joliet, MT — 3 miles away, elevation 3,839 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 59041

JanFebMarAprMayJunJulAugSepOctNovDec

PeasSow outdoors · Apr 17 – May 1

SpinachSow outdoors · Apr 17 – May 8

Broccoli, cabbageStart indoors · Mar 20 – Apr 3

Broccoli, cabbageTransplant · May 8 – May 22

Onion setsPlant outdoors · May 1 – May 15

PotatoesPlant outdoors · May 8 – May 22

LettuceSow outdoors · May 1 – May 15

Carrots, beetsSow outdoors · May 8 – May 22

TomatoesStart indoors · Apr 3 – Apr 17

TomatoesTransplant · Jun 5 – Jun 19

Peppers, eggplantStart indoors · Mar 20 – Apr 3

Peppers, eggplantTransplant · Jun 12 – Jun 26

BeansSow outdoors · Jun 5 – Jun 19

Sweet cornSow outdoors · Jun 5 – Jun 19

Cucumbers, squashSow outdoors · Jun 5 – Jun 19

Fall lettuce, spinachSow outdoors · Jul 21 – Aug 4

GarlicPlant cloves · Sep 1 – Oct 6

Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (May 29) and first fall frost (Sep 15) 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 59041 came on Mar 5 — 33 days earlier than the 1991–2020 average (Apr 7).

average
Apr 72026
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 5a in Montana

548 plants native to the lower 48 states, recorded in Montana, and rated by the USDA to survive −20 °F or colder — the bottom of zone 5a. 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 Joliet, MT.

Soil in Joliet, MT

The soil mapped at the center of ZIP 59041 is Macar — clay loam, well drained.

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

pH7.5slightly alkaline; most vegetables like 6.0–7.0

DrainageWell drainednatural drainage class

Organic matter2%moderate

Hydrologic groupBwater soaks in moderately

Farmland classFarmland of local importanceUSDA classification

Map unit: Macar-Cabba clay loams, 4 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 59041; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Joliet, MT

Summer high86 °Faverage high, July

Winter low10 °Faverage low, January

Hot days29days a year at 90 °F or more

Freezing nights185nights a year at 32 °F or less

Growing degree days1,788base 50 °F — the season’s usable heat

Longest day15 h 41 mindaylight on June 21

Shortest day8 h 42 mindaylight on December 21

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

Precipitation14.5 inper year, rain and melted snow

Snowfall51 inper year; 66 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: Joliet, MT (3 mi away); precipitation: Joliet, MT (3 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

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

Park City, MT · 10 mi

Montana planting zones →

Questions about 59041

What planting zone is ZIP code 59041?

ZIP code 59041 (Joliet, MT) is in USDA hardiness zone 5a on the 2023 map: the coldest night of an average winter reaches −20 to −15 °F (−28.9 to −26.1 °C).

When is the last frost in Joliet, MT?

The median last spring frost (32 °F) near 59041 is May 29; after June 17 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Joliet station.

When is the first frost in Joliet, MT?

The median first fall frost near 59041 is September 15, giving a median frost-free growing season of 107 days.

When should I plant tomatoes in 59041?

Start tomato seeds indoors around Apr 3 – Apr 17 and set transplants outside around Jun 5 – Jun 19, one to three weeks after the median last frost.

How much rain and snow does 59041 get?

About 14.5 inches of precipitation a year and 51 inches of snowfall (NOAA 1991–2020 normals, Joliet station).

How hot do summers get in Joliet, MT?

The average high peaks at 86 °F in July, with about 29 days a year at 90 °F or more.

What kind of soil does 59041 have?

The USDA soil survey maps Macar at the center of ZIP 59041: clay loam, well drained, pH about 7.5 (slightly alkaline).

Did spring come early in Joliet, MT in 2026?

Spring leaf-out near 59041 came on Mar 5 in 2026, 33 days earlier than the 1991–2020 average (Apr 7), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Joliet, MT?

Long-day onions: the longest day near 59041 is 15 h 41 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).

Did the zone for 59041 change?

Yes. The 2012 USDA map put 59041 in zone 4b; the 2023 map puts it in zone 5a. The newer map uses 1991–2020 data and more weather stations.