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

Planting zone for 59844 — Heron, MT

ZIP code 59844 (Heron, Sanders County) is in USDA zone 6b: the coldest winter night averages −5 to 0 °F. The median last spring frost is May 20 and the first fall frost September 20.

Where ZIP 59844 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.

Zone6b−5 to 0 °F

Coldest night−20.6 to −17.8 °C

Last frostMay 20

First frostSep 20

2012 zone6a

Was 6a 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 6b means →

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for Heron, 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 Heron, 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 5only 10% chance of frost after

First fall frostSeptember 20median — 10% chance by Sep 1

Growing season119 daysfrost-free, median

A hard freeze (28 °F) usually ends around May 2 and returns around October 7.

From the NOAA station Heron 2 Nw, MT — 6 miles away, elevation 2,241 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 59844

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 26 – Aug 9

GarlicPlant cloves · Sep 6 – Oct 11

Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (May 20) and first fall frost (Sep 20) 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 59844 came on Apr 24 — about the same time as the 1991–2020 average (Apr 24).

average
Apr 242026
Apr 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).

Soil in Heron, MT

The soil mapped at the center of ZIP 59844 is Phillcher — slightly decomposed plant material, well drained.

TextureSlightly decomposed plant materialtop layer

pH5.0strongly acidic; most vegetables like 6.0–7.0

DrainageWell drainednatural drainage class

Organic matter75%high

Hydrologic groupBwater soaks in moderately

Farmland classNot prime farmlandUSDA classification

Map unit: Phillcher-Rock outcrop complex, mountain 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 59844; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Heron, MT

Summer high82 °Faverage high, July

Winter low23 °Faverage low, January

Hot days12days a year at 90 °F or more

Freezing nights174nights a year at 32 °F or less

Growing degree days1,491base 50 °F — the season’s usable heat

Longest day16 h 03 mindaylight on June 21

Shortest day8 h 22 mindaylight on December 21

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

Precipitation37.1 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: Heron 2 Nw, MT (6 mi away); precipitation: Noxon 4.2 Wnw, MT (5 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

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

598536a

Noxon, MT · 7 mi

838116b

Clark Fork, ID · 13 mi

Trout Creek, MT · 21 mi

Montana planting zones →

Questions about 59844

What planting zone is ZIP code 59844?

ZIP code 59844 (Heron, MT) is in USDA hardiness zone 6b on the 2023 map: the coldest night of an average winter reaches −5 to 0 °F (−20.6 to −17.8 °C).

When is the last frost in Heron, MT?

The median last spring frost (32 °F) near 59844 is May 20; after June 5 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Heron 2 Nw station.

When is the first frost in Heron, MT?

The median first fall frost near 59844 is September 20, giving a median frost-free growing season of 119 days.

When should I plant tomatoes in 59844?

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 59844 get?

About 37.1 inches of precipitation a year (NOAA 1991–2020 normals, Noxon 4.2 Wnw station).

How hot do summers get in Heron, MT?

The average high peaks at 82 °F in July, with about 12 days a year at 90 °F or more.

What kind of soil does 59844 have?

The USDA soil survey maps Phillcher at the center of ZIP 59844: slightly decomposed plant material, well drained, pH about 5.0 (strongly acidic).

Did spring come early in Heron, MT in 2026?

Spring leaf-out near 59844 came on Apr 24 in 2026, about the same as the 1991–2020 average (Apr 24), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Heron, MT?

Long-day onions: the longest day near 59844 is 16 h 03 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).

Did the zone for 59844 change?

Yes. The 2012 USDA map put 59844 in zone 6a; the 2023 map puts it in zone 6b. The newer map uses 1991–2020 data and more weather stations.