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

Planting zone for 59858 — Philipsburg, MT

ZIP code 59858 (Philipsburg, Granite County) is in USDA zone 5a: the coldest winter night averages −20 to −15 °F. The median last spring frost is June 1 and the first fall frost September 14.

Where ZIP 59858 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 frostJun 1

First frostSep 14

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 Philipsburg, 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 Philipsburg, MT

JanFebMarAprMayJunJulAugSepOctNovDec

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

Last spring frostJune 1median — 50% chance of a later frost

Safe for tender plantsJune 25only 10% chance of frost after

First fall frostSeptember 14median — 10% chance by Aug 31

Growing season105 daysfrost-free, median

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

From the NOAA station Anaconda, MT — 28 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 59858

JanFebMarAprMayJunJulAugSepOctNovDec

PeasSow outdoors · Apr 20 – May 4

SpinachSow outdoors · Apr 20 – May 11

Broccoli, cabbageStart indoors · Mar 23 – Apr 6

Broccoli, cabbageTransplant · May 11 – May 25

Onion setsPlant outdoors · May 4 – May 18

PotatoesPlant outdoors · May 11 – May 25

LettuceSow outdoors · May 4 – May 18

Carrots, beetsSow outdoors · May 11 – May 25

TomatoesStart indoors · Apr 6 – Apr 20

TomatoesTransplant · Jun 8 – Jun 22

Peppers, eggplantStart indoors · Mar 23 – Apr 6

Peppers, eggplantTransplant · Jun 15 – Jun 29

BeansSow outdoors · Jun 8 – Jun 22

Sweet cornSow outdoors · Jun 8 – Jun 22

Cucumbers, squashSow outdoors · Jun 8 – Jun 22

Fall lettuce, spinachSow outdoors · Jul 20 – Aug 3

GarlicPlant cloves · Aug 31 – Oct 5

Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (Jun 1) and first fall frost (Sep 14) 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 59858 came on Apr 27 — 9 days earlier than the 1991–2020 average (May 6).

average
May 62026
Apr 27

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 Philipsburg, MT.

Soil in Philipsburg, MT

The soil mapped at the center of ZIP 59858 is Whitore — slightly decomposed plant material, well drained.

TextureSlightly decomposed plant materialtop layer

pH6.5neutral; most vegetables like 6.0–7.0

DrainageWell drainednatural drainage class

Organic matter50%high

Hydrologic groupBwater soaks in moderately

Farmland classNot prime farmlandUSDA classification

Map unit: Whitore gravelly loam, 15 to 35 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 59858; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Philipsburg, MT

Summer high81 °Faverage high, July

Winter low14 °Faverage low, December

Hot days6days a year at 90 °F or more

Freezing nights215nights a year at 32 °F or less

Growing degree days1,159base 50 °F — the season’s usable heat

Longest day15 h 48 mindaylight on June 21

Shortest day8 h 36 mindaylight on December 21

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

Precipitation16.5 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: Phillipsburg Rs, MT (8 mi away); precipitation: Phillipsburg Rs, MT (8 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

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

Corvallis, MT · 24 mi

597625a

Wise River, MT · 24 mi

Gold Creek, MT · 30 mi

597564b

Warm Springs, MT · 31 mi

Montana planting zones →

Questions about 59858

What planting zone is ZIP code 59858?

ZIP code 59858 (Philipsburg, 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 Philipsburg, MT?

The median last spring frost (32 °F) near 59858 is June 1; after June 25 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Anaconda station.

When is the first frost in Philipsburg, MT?

The median first fall frost near 59858 is September 14, giving a median frost-free growing season of 105 days.

When should I plant tomatoes in 59858?

Start tomato seeds indoors around Apr 6 – Apr 20 and set transplants outside around Jun 8 – Jun 22, one to three weeks after the median last frost.

How much rain and snow does 59858 get?

About 16.5 inches of precipitation a year (NOAA 1991–2020 normals, Phillipsburg Rs station).

How hot do summers get in Philipsburg, MT?

The average high peaks at 81 °F in July, with about 6 days a year at 90 °F or more.

What kind of soil does 59858 have?

The USDA soil survey maps Whitore at the center of ZIP 59858: slightly decomposed plant material, well drained, pH about 6.5 (neutral).

Did spring come early in Philipsburg, MT in 2026?

Spring leaf-out near 59858 came on Apr 27 in 2026, 9 days earlier than the 1991–2020 average (May 6), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Philipsburg, MT?

Long-day onions: the longest day near 59858 is 15 h 48 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).

Did the zone for 59858 change?

Yes. The 2012 USDA map put 59858 in zone 4b; the 2023 map puts it in zone 5a. The newer map uses 1991–2020 data and more weather stations.