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

Planting zone for 59446 — Geraldine, MT

ZIP code 59446 (Geraldine, Chouteau County) is in USDA zone 4b: the coldest winter night averages −25 to −20 °F. The median last spring frost is May 14 and the first fall frost September 26.

Where ZIP 59446 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.

Zone4b−25 to −20 °F
Coldest night−31.7 to −28.9 °C
Last frostMay 14
First frostSep 26
2012 zone4a

Was 4a 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 4b means →

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for Geraldine, 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 Geraldine, MT

JanFebMarAprMayJunJulAugSepOctNovDec
Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free
Last spring frostMay 14median — 50% chance of a later frost
Safe for tender plantsMay 28only 10% chance of frost after
First fall frostSeptember 26median — 10% chance by Sep 13
Growing season134 daysfrost-free, median

A hard freeze (28 °F) usually ends around May 3 and returns around October 4.

From the NOAA station Geraldine, MT — 6 miles away, elevation 3,146 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 59446

JanFebMarAprMayJunJulAugSepOctNovDec
PeasSow outdoors · Apr 2 – Apr 16
SpinachSow outdoors · Apr 2 – Apr 23
Broccoli, cabbageStart indoors · Mar 5 – Mar 19
Broccoli, cabbageTransplant · Apr 23 – May 7
Onion setsPlant outdoors · Apr 16 – Apr 30
PotatoesPlant outdoors · Apr 23 – May 7
LettuceSow outdoors · Apr 16 – Apr 30
Carrots, beetsSow outdoors · Apr 23 – May 7
TomatoesStart indoors · Mar 19 – Apr 2
TomatoesTransplant · May 21 – Jun 4
Peppers, eggplantStart indoors · Mar 5 – Mar 19
Peppers, eggplantTransplant · May 28 – Jun 11
BeansSow outdoors · May 21 – Jun 4
Sweet cornSow outdoors · May 21 – Jun 4
Cucumbers, squashSow outdoors · May 21 – Jun 4
Fall lettuce, spinachSow outdoors · Aug 1 – Aug 15
GarlicPlant cloves · Sep 12 – Oct 17
Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (May 14) and first fall frost (Sep 26) 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 59446 came on Mar 12 — 26 days earlier than the 1991–2020 average (Apr 7).

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 4b in Montana

506 plants native to the lower 48 states, recorded in Montana, and rated by the USDA to survive −25 °F or colder — the bottom of zone 4b. Each links to its USDA PLANTS profile.

Trees 23

American elm120 ft · blooms early spring · medium shade tolerance · to −46 °Fbalsam poplar80 ft · blooms late spring · high shade tolerance · to −79 °Fblack locust60 ft · blooms spring · high shade tolerance · to −37 °Fboxelder60 ft · blooms early spring · low shade tolerance · to −46 °FDouglas-fir200 ft · blooms mid spring · medium shade tolerance · to −33 °Feastern cottonwood190 ft · blooms spring · high shade tolerance · to −43 °F

Shrubs 87

alderleaf buckthorn3 ft · blooms late spring · low shade tolerance · to −33 °Falderleaf mountain mahogany15 ft · blooms late spring · medium shade tolerance · to −41 °Falpine laurel1 ft · blooms late spring · low shade tolerance · to −28 °FAmerican black currant3 ft · blooms early spring · to −46 °FAmerican plum24 ft · blooms mid spring · high shade tolerance · to −38 °Fantelope bitterbrush6 ft · blooms early spring · medium shade tolerance · to −36 °F

Wildflowers & perennials 229

alkali buttercup1 ft · blooms late spring · low shade tolerance · to −38 °Falpine bistort1 ft · blooms mid spring · high shade tolerance · to −38 °Falpine mountainsorrel1 ft · blooms mid summer · medium shade tolerance · to −43 °Falpine sweetvetch2 ft · blooms early summer · high shade tolerance · to −62 °FAmerican alpine speedwell1 ft · blooms summer · medium shade tolerance · to −28 °FAmerican bistort1.5 ft · blooms mid spring · high shade tolerance · to −38 °F

Grasses 155

Alaska oniongrass3 ft · blooms mid spring · low shade tolerance · to −33 °Falkali cordgrass3 ft · blooms late summer · high shade tolerance · to −38 °Falkali sacaton3 ft · blooms mid summer · high shade tolerance · to −38 °FAlpine Meadow-Foxtail0.5 ft · blooms mid spring · medium shade tolerance · to −33 °Falpine timothy1.4 ft · blooms late spring · medium shade tolerance · to −43 °Fanalogue sedge1.5 ft · blooms late spring · medium shade tolerance · to −38 °F

Vines 3

American bittersweet15 ft · blooms spring · low shade tolerance · to −38 °Friverbank grape45 ft · blooms late spring · medium shade tolerance · to −33 °Fwestern white clematis1 ft · blooms mid summer · medium shade tolerance · to −38 °F

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 Geraldine, MT.

Soil in Geraldine, MT

The soil mapped at the center of ZIP 59446 is Vida — clay loam, well drained.

TextureClay loamholds water and nutrients; slow to drain and warm up
pH7.0neutral; most vegetables like 6.0–7.0
DrainageWell drainednatural drainage class
Organic matter3.5%moderate
Hydrologic groupCwater soaks in slowly
Farmland classNot prime farmlandUSDA classification

Map unit: Vida-Bearpaw-Zahill clay loams, 4 to 15 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 59446; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Geraldine, MT

Summer high86 °Faverage high, July
Winter low15 °Faverage low, January
Hot days31days a year at 90 °F or more
Freezing nights155nights a year at 32 °F or less
Growing degree days2,280base 50 °F — the season’s usable heat
Longest day16 h 00 mindaylight on June 21
Shortest day8 h 25 mindaylight on December 21
Onions to growLong-daysummer days reach 15+ hours, enough for long-day varieties (intermediate types work too)
Precipitation16.9 inper year, rain and melted snow

Average high and low, by month

0°10°20°30°40°50°60°70°80°90°100°32 °FJanuary: average high 37 °F, low 15 °F 37°15° JanFebruary: average high 40 °F, low 16 °F 40°16° FebMarch: average high 50 °F, low 24 °F 50°24° MarApril: average high 59 °F, low 32 °F 59°32° AprMay: average high 68 °F, low 41 °F 68°41° MayJune: average high 76 °F, low 49 °F 76°49° JunJuly: average high 86 °F, low 55 °F 86°55° JulAugust: average high 86 °F, low 53 °F 86°53° AugSeptember: average high 75 °F, low 45 °F 75°45° SepOctober: average high 60 °F, low 34 °F 60°34° OctNovember: average high 46 °F, low 24 °F 46°24° NovDecember: average high 39 °F, low 16 °F 39°16° Dec

Precipitation by month inches

0″1″2″3″4″January: 0.60 in precipitation 0.6 JanFebruary: 0.57 in precipitation 0.6 FebMarch: 0.82 in precipitation 0.8 MarApril: 2.10 in precipitation 2.1 AprMay: 2.69 in precipitation 2.7 MayJune: 3.23 in precipitation 3.2 JunJuly: 1.71 in precipitation 1.7 JulAugust: 1.28 in precipitation 1.3 AugSeptember: 1.49 in precipitation 1.5 SepOctober: 1.14 in precipitation 1.1 OctNovember: 0.63 in precipitation 0.6 NovDecember: 0.59 in precipitation 0.6 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Geraldine, MT (6 mi away); precipitation: Geraldine, MT (6 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.

594244b
Coffee Creek, MT · 21 mi
594304b
Denton, MT · 23 mi
594504b
Highwood, MT · 28 mi
595204a
Big Sandy, MT · 29 mi
594474b
Geyser, MT · 29 mi
594424a
Fort Benton, MT · 30 mi
594604a
Loma, MT · 34 mi
594624b
Moccasin, MT · 40 mi

Montana planting zones →

Questions about 59446

What planting zone is ZIP code 59446?

ZIP code 59446 (Geraldine, MT) is in USDA hardiness zone 4b on the 2023 map: the coldest night of an average winter reaches −25 to −20 °F (−31.7 to −28.9 °C).

When is the last frost in Geraldine, MT?

The median last spring frost (32 °F) near 59446 is May 14; after May 28 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Geraldine station.

When is the first frost in Geraldine, MT?

The median first fall frost near 59446 is September 26, giving a median frost-free growing season of 134 days.

When should I plant tomatoes in 59446?

Start tomato seeds indoors around Mar 19 – Apr 2 and set transplants outside around May 21 – Jun 4, one to three weeks after the median last frost.

How much rain and snow does 59446 get?

About 16.9 inches of precipitation a year (NOAA 1991–2020 normals, Geraldine station).

How hot do summers get in Geraldine, MT?

The average high peaks at 86 °F in July, with about 31 days a year at 90 °F or more.

What kind of soil does 59446 have?

The USDA soil survey maps Vida at the center of ZIP 59446: clay loam, well drained, pH about 7.0 (neutral).

Did spring come early in Geraldine, MT in 2026?

Spring leaf-out near 59446 came on Mar 12 in 2026, 26 days earlier than the 1991–2020 average (Apr 7), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Geraldine, MT?

Long-day onions: the longest day near 59446 is 16 h 00 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).

Did the zone for 59446 change?

Yes. The 2012 USDA map put 59446 in zone 4a; the 2023 map puts it in zone 4b. The newer map uses 1991–2020 data and more weather stations.