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

Planting zone for 59255 — Poplar, MT

ZIP code 59255 (Poplar, Roosevelt County) is in USDA zone 4a: the coldest winter night averages −30 to −25 °F. The median last spring frost is May 24 and the first fall frost September 14.

Where ZIP 59255 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 24
First frostSep 14
2012 zone3b

Was 3b 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 4a means →

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for Poplar, 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 Poplar, MT

JanFebMarAprMayJunJulAugSepOctNovDec
Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free
Last spring frostMay 24median — 50% chance of a later frost
Safe for tender plantsJune 6only 10% chance of frost after
First fall frostSeptember 14median — 10% chance by Sep 1
Growing season110 daysfrost-free, median

A hard freeze (28 °F) usually ends around May 14 and returns around September 22.

From the NOAA station Wolf Point 29 Ene, MT — 6 miles away, elevation 2,087 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 59255

JanFebMarAprMayJunJulAugSepOctNovDec
PeasSow outdoors · Apr 12 – Apr 26
SpinachSow outdoors · Apr 12 – May 3
Broccoli, cabbageStart indoors · Mar 15 – Mar 29
Broccoli, cabbageTransplant · May 3 – May 17
Onion setsPlant outdoors · Apr 26 – May 10
PotatoesPlant outdoors · May 3 – May 17
LettuceSow outdoors · Apr 26 – May 10
Carrots, beetsSow outdoors · May 3 – May 17
TomatoesStart indoors · Mar 29 – Apr 12
TomatoesTransplant · May 31 – Jun 14
Peppers, eggplantStart indoors · Mar 15 – Mar 29
Peppers, eggplantTransplant · Jun 7 – Jun 21
BeansSow outdoors · May 31 – Jun 14
Sweet cornSow outdoors · May 31 – Jun 14
Cucumbers, squashSow outdoors · May 31 – Jun 14
Fall lettuce, spinachSow outdoors · Jul 20 – Aug 3
GarlicPlant cloves · Aug 31 – Oct 5
Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (May 24) and first fall frost (Sep 14) 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 59255 came on Apr 20 — about the same time as the 1991–2020 average (Apr 18).

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 Poplar, MT

The soil mapped at the center of ZIP 59255 is Vida — loam, well drained.

TextureLoama good balance for most vegetables
pH7.2neutral; 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-Zahill loams, 2 to 8 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 59255; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Poplar, MT

Summer high84 °Faverage high, July
Winter low0 °Faverage low, January
Hot days23days a year at 90 °F or more
Freezing nights206nights a year at 32 °F or less
Growing degree days1,888base 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)
Precipitation14.2 inper year, rain and melted snow

Average high and low, by month

−10°0°10°20°30°40°50°60°70°80°90°32 °FJanuary: average high 23 °F, low 0 °F 23°0° JanFebruary: average high 28 °F, low 5 °F 28°5° FebMarch: average high 40 °F, low 16 °F 40°16° MarApril: average high 56 °F, low 27 °F 56°27° AprMay: average high 67 °F, low 38 °F 67°38° MayJune: average high 76 °F, low 48 °F 76°48° JunJuly: average high 84 °F, low 53 °F 84°53° JulAugust: average high 84 °F, low 51 °F 84°51° AugSeptember: average high 73 °F, low 40 °F 73°40° SepOctober: average high 56 °F, low 27 °F 56°27° OctNovember: average high 39 °F, low 14 °F 39°14° NovDecember: average high 27 °F, low 3 °F 27°3° Dec

Precipitation by month inches

0″1″2″3″January: 0.43 in precipitation 0.4 JanFebruary: 0.30 in precipitation 0.3 FebMarch: 0.59 in precipitation 0.6 MarApril: 1.03 in precipitation 1.0 AprMay: 2.19 in precipitation 2.2 MayJune: 2.94 in precipitation 2.9 JunJuly: 2.57 in precipitation 2.6 JulAugust: 1.38 in precipitation 1.4 AugSeptember: 1.07 in precipitation 1.1 SepOctober: 0.87 in precipitation 0.9 OctNovember: 0.43 in precipitation 0.4 NovDecember: 0.39 in precipitation 0.4 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Wolf Point 29 Ene, MT (6 mi away); precipitation: Wolf Point 29 Ene, MT (6 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.

592134a
Brockton, MT · 13 mi
592014a
Wolf Point, MT · 23 mi
592744a
Vida, MT · 30 mi
592264a
Froid, MT · 30 mi
592224a
Flaxville, MT · 32 mi
592583b
Reserve, MT · 33 mi
592473b
Medicine Lake, MT · 35 mi
592594a
Richey, MT · 38 mi

Montana planting zones →

Questions about 59255

What planting zone is ZIP code 59255?

ZIP code 59255 (Poplar, 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 Poplar, MT?

The median last spring frost (32 °F) near 59255 is May 24; after June 6 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Wolf Point 29 Ene station.

When is the first frost in Poplar, MT?

The median first fall frost near 59255 is September 14, giving a median frost-free growing season of 110 days.

When should I plant tomatoes in 59255?

Start tomato seeds indoors around Mar 29 – Apr 12 and set transplants outside around May 31 – Jun 14, one to three weeks after the median last frost.

How much rain and snow does 59255 get?

About 14.2 inches of precipitation a year (NOAA 1991–2020 normals, Wolf Point 29 Ene station).

How hot do summers get in Poplar, MT?

The average high peaks at 84 °F in July, with about 23 days a year at 90 °F or more.

What kind of soil does 59255 have?

The USDA soil survey maps Vida at the center of ZIP 59255: loam, well drained, pH about 7.2 (neutral).

Did spring come early in Poplar, MT in 2026?

Spring leaf-out near 59255 came on Apr 20 in 2026, about the same as the 1991–2020 average (Apr 18), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Poplar, MT?

Long-day onions: the longest day near 59255 is 16 h 05 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).

Did the zone for 59255 change?

Yes. The 2012 USDA map put 59255 in zone 3b; the 2023 map puts it in zone 4a. The newer map uses 1991–2020 data and more weather stations.