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

Planting zone for 59903 — Kalispell, MT

ZIP code 59903 (Kalispell, Flathead County) is in USDA zone 5b: the coldest winter night averages −15 to −10 °F. The median last spring frost is May 31 and the first fall frost September 10.

Where ZIP 59903 is

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.

Zone5b−15 to −10 °F

Coldest night−26.1 to −23.3 °C

Last frostMay 31

First frostSep 10

2012 zone5a

Was 5a 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 5b means →

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for Kalispell, 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 Kalispell, MT

JanFebMarAprMayJunJulAugSepOctNovDec

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

Last spring frostMay 31median — 50% chance of a later frost

Safe for tender plantsJune 22only 10% chance of frost after

First fall frostSeptember 10median — 10% chance by Aug 26

Growing season100 daysfrost-free, median

A hard freeze (28 °F) usually ends around May 10 and returns around September 27.

From the NOAA station Kalispell Glacier Airport, MT — 9 miles away, elevation 2,956 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 59903

JanFebMarAprMayJunJulAugSepOctNovDec

PeasSow outdoors · Apr 19 – May 3

SpinachSow outdoors · Apr 19 – May 10

Broccoli, cabbageStart indoors · Mar 22 – Apr 5

Broccoli, cabbageTransplant · May 10 – May 24

Onion setsPlant outdoors · May 3 – May 17

PotatoesPlant outdoors · May 10 – May 24

LettuceSow outdoors · May 3 – May 17

Carrots, beetsSow outdoors · May 10 – May 24

TomatoesStart indoors · Apr 5 – Apr 19

TomatoesTransplant · Jun 7 – Jun 21

Peppers, eggplantStart indoors · Mar 22 – Apr 5

Peppers, eggplantTransplant · Jun 14 – Jun 28

BeansSow outdoors · Jun 7 – Jun 21

Sweet cornSow outdoors · Jun 7 – Jun 21

Cucumbers, squashSow outdoors · Jun 7 – Jun 21

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 (May 31) 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 59903 came on Apr 12 — 10 days earlier than the 1991–2020 average (Apr 22).

average
Apr 222026
Apr 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 5b in Montana

561 plants native to the lower 48 states, recorded in Montana, and rated by the USDA to survive −15 °F or colder — the bottom of zone 5b. 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 Kalispell, MT.

Soil in Kalispell, MT

The soil mapped at the center of ZIP 59903 is Typic Eutroboralfs — slightly decomposed plant material.

TextureSlightly decomposed plant materialtop layer

pH6.5neutral; most vegetables like 6.0–7.0

Organic matter50%high

Hydrologic groupBwater soaks in moderately

Farmland classNot prime farmlandUSDA classification

Map unit: Typic Eutroboralfs, silty till substratum, hilly.

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 59903; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Kalispell, MT

Summer high82 °Faverage high, July

Winter low16 °Faverage low, January

Hot days14days a year at 90 °F or more

Freezing nights187nights a year at 32 °F or less

Growing degree days1,425base 50 °F — the season’s usable heat

Longest day16 h 05 mindaylight on June 21

Shortest day8 h 20 mindaylight on December 21

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

Precipitation17.2 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: Kalispell Glacier Airport, MT (9 mi away); precipitation: Kalispell 10.1 Sw, MT (9 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

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

Whitefish, MT · 15 mi

Columbia Falls, MT · 19 mi

599195b

Hungry Horse, MT · 20 mi

All 3 ZIP codes in Kalispell → · Montana planting zones →

Questions about 59903

What planting zone is ZIP code 59903?

ZIP code 59903 (Kalispell, MT) is in USDA hardiness zone 5b on the 2023 map: the coldest night of an average winter reaches −15 to −10 °F (−26.1 to −23.3 °C).

When is the last frost in Kalispell, MT?

The median last spring frost (32 °F) near 59903 is May 31; after June 22 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Kalispell Glacier Airport station.

When is the first frost in Kalispell, MT?

The median first fall frost near 59903 is September 10, giving a median frost-free growing season of 100 days.

When should I plant tomatoes in 59903?

Start tomato seeds indoors around Apr 5 – Apr 19 and set transplants outside around Jun 7 – Jun 21, one to three weeks after the median last frost.

How much rain and snow does 59903 get?

About 17.2 inches of precipitation a year (NOAA 1991–2020 normals, Kalispell 10.1 Sw station).

How hot do summers get in Kalispell, MT?

The average high peaks at 82 °F in July, with about 14 days a year at 90 °F or more.

What kind of soil does 59903 have?

The USDA soil survey maps Typic Eutroboralfs at the center of ZIP 59903: slightly decomposed plant material, pH about 6.5 (neutral).

Did spring come early in Kalispell, MT in 2026?

Spring leaf-out near 59903 came on Apr 12 in 2026, 10 days earlier than the 1991–2020 average (Apr 22), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Kalispell, MT?

Long-day onions: the longest day near 59903 is 16 h 05 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).

Did the zone for 59903 change?

Yes. The 2012 USDA map put 59903 in zone 5a; the 2023 map puts it in zone 5b. The newer map uses 1991–2020 data and more weather stations.