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

Planting zone for 59326 — Fallon, MT

ZIP code 59326 (Fallon, Prairie County) is in USDA zone 4a: the coldest winter night averages −30 to −25 °F. The median last spring frost is May 20 and the first fall frost September 22.

Where ZIP 59326 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 20

First frostSep 22

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 Fallon, 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 Fallon, MT

JanFebMarAprMayJunJulAugSepOctNovDec

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

Last spring frostMay 20median — 50% chance of a later frost

Safe for tender plantsJune 2only 10% chance of frost after

First fall frostSeptember 22median — 10% chance by Sep 7

Growing season124 daysfrost-free, median

A hard freeze (28 °F) usually ends around May 7 and returns around October 1.

From the NOAA station Mildred 5 N, MT — 5 miles away, elevation 2,484 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 59326

JanFebMarAprMayJunJulAugSepOctNovDec

PeasSow outdoors · Apr 8 – Apr 22

SpinachSow outdoors · Apr 8 – Apr 29

Broccoli, cabbageStart indoors · Mar 11 – Mar 25

Broccoli, cabbageTransplant · Apr 29 – May 13

Onion setsPlant outdoors · Apr 22 – May 6

PotatoesPlant outdoors · Apr 29 – May 13

LettuceSow outdoors · Apr 22 – May 6

Carrots, beetsSow outdoors · Apr 29 – May 13

TomatoesStart indoors · Mar 25 – Apr 8

TomatoesTransplant · May 27 – Jun 10

Peppers, eggplantStart indoors · Mar 11 – Mar 25

Peppers, eggplantTransplant · Jun 3 – Jun 17

BeansSow outdoors · May 27 – Jun 10

Sweet cornSow outdoors · May 27 – Jun 10

Cucumbers, squashSow outdoors · May 27 – Jun 10

Fall lettuce, spinachSow outdoors · Jul 28 – Aug 11

GarlicPlant cloves · Sep 8 – Oct 13

Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (May 20) and first fall frost (Sep 22) 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 59326 came on Mar 24 — 18 days earlier than the 1991–2020 average (Apr 11).

average
Apr 112026
Mar 24

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 Fallon, MT.

Soil in Fallon, MT

The soil mapped at the center of ZIP 59326 is Lonna — silt loam, well drained.

TextureSilt loama good balance for most vegetables

pH7.9alkaline; most vegetables like 6.0–7.0

DrainageWell drainednatural drainage class

Organic matter2%moderate

Hydrologic groupCwater soaks in slowly

Farmland classNot prime farmlandUSDA classification

Map unit: Lonna-Cambeth-Cabbart silt loams, 12 to 25 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 59326; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Fallon, MT

Summer high87 °Faverage high, July

Winter low6 °Faverage low, January

Hot days35days a year at 90 °F or more

Freezing nights191nights a year at 32 °F or less

Growing degree days2,279base 50 °F — the season’s usable heat

Longest day15 h 52 mindaylight on June 21

Shortest day8 h 32 mindaylight on December 21

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

Precipitation14.3 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: Mildred 5 N, MT (5 mi away); precipitation: Mildred 5 N, MT (5 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.

Montana planting zones →

Questions about 59326

What planting zone is ZIP code 59326?

ZIP code 59326 (Fallon, 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 Fallon, MT?

The median last spring frost (32 °F) near 59326 is May 20; after June 2 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Mildred 5 N station.

When is the first frost in Fallon, MT?

The median first fall frost near 59326 is September 22, giving a median frost-free growing season of 124 days.

When should I plant tomatoes in 59326?

Start tomato seeds indoors around Mar 25 – Apr 8 and set transplants outside around May 27 – Jun 10, one to three weeks after the median last frost.

How much rain and snow does 59326 get?

About 14.3 inches of precipitation a year (NOAA 1991–2020 normals, Mildred 5 N station).

How hot do summers get in Fallon, MT?

The average high peaks at 87 °F in July, with about 35 days a year at 90 °F or more.

What kind of soil does 59326 have?

The USDA soil survey maps Lonna at the center of ZIP 59326: silt loam, well drained, pH about 7.9 (alkaline).

Did spring come early in Fallon, MT in 2026?

Spring leaf-out near 59326 came on Mar 24 in 2026, 18 days earlier than the 1991–2020 average (Apr 11), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Fallon, MT?

Long-day onions: the longest day near 59326 is 15 h 52 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).