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

Planting zone for 59213 — Brockton, MT

ZIP code 59213 (Brockton, 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 59213 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 Brockton, 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 Brockton, 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 — 13 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 59213

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 59213 came on Apr 20 — 3 days later than the 1991–2020 average (Apr 17).

average
Apr 172026
Apr 20

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 Brockton, MT.

Soil in Brockton, MT

The soil mapped at the center of ZIP 59213 is Zahill — loam, well drained.

TextureLoama good balance for most vegetables

pH7.9alkaline; 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: Zahill-Vida 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 59213; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Brockton, 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

Precipitation by month inches

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Wolf Point 29 Ene, MT (13 mi away); precipitation: Wolf Point 29 Ene, MT (13 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.

Culbertson, MT · 20 mi

592423b

Homestead, MT · 26 mi

592473b

Medicine Lake, MT · 28 mi

Montana planting zones →

Questions about 59213

What planting zone is ZIP code 59213?

ZIP code 59213 (Brockton, 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 Brockton, MT?

The median last spring frost (32 °F) near 59213 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 Brockton, MT?

The median first fall frost near 59213 is September 14, giving a median frost-free growing season of 110 days.

When should I plant tomatoes in 59213?

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 59213 get?

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

How hot do summers get in Brockton, 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 59213 have?

The USDA soil survey maps Zahill at the center of ZIP 59213: loam, well drained, pH about 7.9 (alkaline).

Did spring come early in Brockton, MT in 2026?

Spring leaf-out near 59213 came on Apr 20 in 2026, 3 days later than the 1991–2020 average (Apr 17), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Brockton, MT?

Long-day onions: the longest day near 59213 is 16 h 05 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).

Did the zone for 59213 change?

Yes. The 2012 USDA map put 59213 in zone 3b; the 2023 map puts it in zone 4a. The newer map uses 1991–2020 data and more weather stations.