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

Planting zone for 59544 — Whitewater, MT

ZIP code 59544 (Whitewater, Phillips County) is in USDA zone 3b: the coldest winter night averages −35 to −30 °F. The median last spring frost is May 19 and the first fall frost September 22.

Where ZIP 59544 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.

Zone3b−35 to −30 °F
Coldest night−37.2 to −34.4 °C
Last frostMay 19
First frostSep 22
2012 zone3b

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 3b means →

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for Whitewater, 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 Whitewater, MT

JanFebMarAprMayJunJulAugSepOctNovDec
Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free
Last spring frostMay 19median — 50% chance of a later frost
Safe for tender plantsJune 2only 10% chance of frost after
First fall frostSeptember 22median — 10% chance by Sep 9
Growing season124 daysfrost-free, median

A hard freeze (28 °F) usually ends around May 8 and returns around September 30.

From the NOAA station Port Of Morgan, MT — 19 miles away, elevation 2,832 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 59544

JanFebMarAprMayJunJulAugSepOctNovDec
PeasSow outdoors · Apr 7 – Apr 21
SpinachSow outdoors · Apr 7 – Apr 28
Broccoli, cabbageStart indoors · Mar 10 – Mar 24
Broccoli, cabbageTransplant · Apr 28 – May 12
Onion setsPlant outdoors · Apr 21 – May 5
PotatoesPlant outdoors · Apr 28 – May 12
LettuceSow outdoors · Apr 21 – May 5
Carrots, beetsSow outdoors · Apr 28 – May 12
TomatoesStart indoors · Mar 24 – Apr 7
TomatoesTransplant · May 26 – Jun 9
Peppers, eggplantStart indoors · Mar 10 – Mar 24
Peppers, eggplantTransplant · Jun 2 – Jun 16
BeansSow outdoors · May 26 – Jun 9
Sweet cornSow outdoors · May 26 – Jun 9
Cucumbers, squashSow outdoors · May 26 – Jun 9
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 19) 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 59544 came on Apr 21 — about the same time as the 1991–2020 average (Apr 19).

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 3b in Montana

304 plants native to the lower 48 states, recorded in Montana, and rated by the USDA to survive −35 °F or colder — the bottom of zone 3b. Each links to its USDA PLANTS profile.

Trees 17

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 °Feastern cottonwood190 ft · blooms spring · high shade tolerance · to −43 °FEngelmann spruce120 ft · blooms late spring · low shade tolerance · to −50 °F

Shrubs 60

alderleaf mountain mahogany15 ft · blooms late spring · medium shade tolerance · to −41 °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 °FBarclay's willow15 ft · high shade tolerance · to −43 °Fbeaked hazelnut15 ft · blooms early spring · low shade tolerance · to −47 °F

Wildflowers & perennials 109

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 bistort1.5 ft · blooms mid spring · high shade tolerance · to −38 °FAmerican licorice4 ft · blooms late spring · medium shade tolerance · to −38 °F

Grasses 109

alkali cordgrass3 ft · blooms late summer · high shade tolerance · to −38 °Falkali sacaton3 ft · blooms mid summer · high shade tolerance · to −38 °Falpine timothy1.4 ft · blooms late spring · medium shade tolerance · to −43 °Fanalogue sedge1.5 ft · blooms late spring · medium shade tolerance · to −38 °Farctic bluegrass2 ft · high shade tolerance · to −62 °Fawlfruit sedge4 ft · blooms mid spring · low shade tolerance · to −38 °F

Vines 2

American bittersweet15 ft · blooms spring · low shade tolerance · to −38 °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 Whitewater, MT.

Soil in Whitewater, MT

The soil mapped at the center of ZIP 59544 is Hillon — clay loam, well drained.

TextureClay loamholds water and nutrients; slow to drain and warm up
pH8.0alkaline; most vegetables like 6.0–7.0
DrainageWell drainednatural drainage class
Organic matter1.5%low — add compost
Hydrologic groupCwater soaks in slowly
Farmland classNot prime farmlandUSDA classification

Map unit: Hillon-Kevin 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 59544; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Whitewater, MT

Summer high83 °Faverage high, July
Winter low4 °Faverage low, January
Hot days16days a year at 90 °F or more
Freezing nights189nights a year at 32 °F or less
Growing degree days1,940base 50 °F — the season’s usable heat
Longest day16 h 10 mindaylight on June 21
Shortest day8 h 15 mindaylight on December 21
Onions to growLong-daysummer days reach 15+ hours, enough for long-day varieties (intermediate types work too)
Precipitation12.5 inper year, rain and melted snow
Snowfall10 inper year

Average high and low, by month

−10°0°10°20°30°40°50°60°70°80°90°32 °FJanuary: average high 23 °F, low 4 °F 23°4° JanFebruary: average high 28 °F, low 8 °F 28°8° FebMarch: average high 40 °F, low 18 °F 40°18° MarApril: average high 56 °F, low 30 °F 56°30° AprMay: average high 67 °F, low 39 °F 67°39° MayJune: average high 74 °F, low 48 °F 74°48° JunJuly: average high 83 °F, low 54 °F 83°54° JulAugust: average high 83 °F, low 52 °F 83°52° AugSeptember: average high 72 °F, low 43 °F 72°43° SepOctober: average high 56 °F, low 31 °F 56°31° OctNovember: average high 38 °F, low 19 °F 38°19° NovDecember: average high 26 °F, low 8 °F 26°8° Dec

Precipitation by month inches · ❄ = snowfall

0″1″2″3″January: 0.52 in precipitation, 1.4 in snowfall 0.5❄1 JanFebruary: 0.28 in precipitation, 2.4 in snowfall 0.3❄2 FebMarch: 0.39 in precipitation, 0.8 in snowfall 0.4❄1 MarApril: 1.00 in precipitation, 0.4 in snowfall 1.0 AprMay: 1.84 in precipitation, 0.3 in snowfall 1.8 MayJune: 2.78 in precipitation 2.8 JunJuly: 1.34 in precipitation 1.3 JulAugust: 1.35 in precipitation 1.4 AugSeptember: 1.17 in precipitation 1.2 SepOctober: 0.89 in precipitation, 0.8 in snowfall 0.9❄1 OctNovember: 0.52 in precipitation, 2 in snowfall 0.5❄2 NovDecember: 0.44 in precipitation, 1.8 in snowfall 0.4❄2 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Port Of Morgan, MT (19 mi away); precipitation: Whitewater, MT (4 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.

595373b
Loring, MT · 20 mi
592613b
Saco, MT · 20 mi
592413b
Hinsdale, MT · 33 mi
595424a
Turner, MT · 36 mi
592503b
Opheim, MT · 42 mi
592734a
Vandalia, MT · 44 mi
595294a
Hogeland, MT · 51 mi
592314a
Saint Marie, MT · 54 mi

Montana planting zones →

Questions about 59544

What planting zone is ZIP code 59544?

ZIP code 59544 (Whitewater, MT) is in USDA hardiness zone 3b on the 2023 map: the coldest night of an average winter reaches −35 to −30 °F (−37.2 to −34.4 °C).

When is the last frost in Whitewater, MT?

The median last spring frost (32 °F) near 59544 is May 19; after June 2 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Port Of Morgan station.

When is the first frost in Whitewater, MT?

The median first fall frost near 59544 is September 22, giving a median frost-free growing season of 124 days.

When should I plant tomatoes in 59544?

Start tomato seeds indoors around Mar 24 – Apr 7 and set transplants outside around May 26 – Jun 9, one to three weeks after the median last frost.

How much rain and snow does 59544 get?

About 12.5 inches of precipitation a year and 10 inches of snowfall (NOAA 1991–2020 normals, Whitewater station).

How hot do summers get in Whitewater, MT?

The average high peaks at 83 °F in July, with about 16 days a year at 90 °F or more.

What kind of soil does 59544 have?

The USDA soil survey maps Hillon at the center of ZIP 59544: clay loam, well drained, pH about 8.0 (alkaline).

Did spring come early in Whitewater, MT in 2026?

Spring leaf-out near 59544 came on Apr 21 in 2026, about the same as the 1991–2020 average (Apr 19), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Whitewater, MT?

Long-day onions: the longest day near 59544 is 16 h 10 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).