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

Planting zone for 58620 — Amidon, ND

ZIP code 58620 (Amidon, Slope County) is in USDA zone 4b: the coldest winter night averages −25 to −20 °F. The median last spring frost is May 12 and the first fall frost September 29.

Where ZIP 58620 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 12

First frostSep 29

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 Amidon, ND…

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 Amidon, ND

JanFebMarAprMayJunJulAugSepOctNovDec

Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free

Last spring frostMay 12median — 50% chance of a later frost

Safe for tender plantsMay 28only 10% chance of frost after

First fall frostSeptember 29median — 10% chance by Sep 14

Growing season136 daysfrost-free, median

A hard freeze (28 °F) usually ends around May 3 and returns around October 6.

From the NOAA station Amidon, ND — 2 miles away, elevation 2,910 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 58620

JanFebMarAprMayJunJulAugSepOctNovDec

PeasSow outdoors · Mar 31 – Apr 14

SpinachSow outdoors · Mar 31 – Apr 21

Broccoli, cabbageStart indoors · Mar 3 – Mar 17

Broccoli, cabbageTransplant · Apr 21 – May 5

Onion setsPlant outdoors · Apr 14 – Apr 28

PotatoesPlant outdoors · Apr 21 – May 5

LettuceSow outdoors · Apr 14 – Apr 28

Carrots, beetsSow outdoors · Apr 21 – May 5

TomatoesStart indoors · Mar 17 – Mar 31

TomatoesTransplant · May 19 – Jun 2

Peppers, eggplantStart indoors · Mar 3 – Mar 17

Peppers, eggplantTransplant · May 26 – Jun 9

BeansSow outdoors · May 19 – Jun 2

Sweet cornSow outdoors · May 19 – Jun 2

Cucumbers, squashSow outdoors · May 19 – Jun 2

Fall lettuce, spinachSow outdoors · Aug 4 – Aug 18

GarlicPlant cloves · Sep 15 – Oct 20

Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (May 12) and first fall frost (Sep 29) 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 58620 came on Apr 8 — 7 days earlier than the 1991–2020 average (Apr 15).

average
Apr 152026
Apr 8

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 North Dakota

372 plants native to the lower 48 states, recorded in North Dakota, and rated by the USDA to survive −25 °F or colder — the bottom of zone 4b. 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 Amidon, ND.

Soil in Amidon, ND

The soil mapped at the center of ZIP 58620 is Shambo — loam, well drained.

TextureLoama good balance for most vegetables

pH6.3slightly acidic; most vegetables like 6.0–7.0

DrainageWell drainednatural drainage class

Organic matter3.5%moderate

Hydrologic groupBwater soaks in moderately

Farmland classFarmland of statewide importanceUSDA classification

Map unit: Shambo loam, 2 to 6 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 58620; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Amidon, ND

Summer high86 °Faverage high, July

Winter low7 °Faverage low, January

Hot days31days a year at 90 °F or more

Freezing nights181nights a year at 32 °F or less

Growing degree days2,346base 50 °F — the season’s usable heat

Longest day15 h 49 mindaylight on June 21

Shortest day8 h 34 mindaylight on December 21

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

Precipitation17.1 inper year, rain and melted snow

Snowfall48 inper year; 99 days with snow on the ground

Average high and low, by month

Precipitation by month inches · ❄ = snowfall

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Amidon, ND (2 mi away); precipitation: Bowman, ND (22 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

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

586474b

New England, ND · 19 mi

586554b

South Heart, ND · 23 mi

Sentinel Butte, ND · 30 mi

North Dakota planting zones →

Questions about 58620

What planting zone is ZIP code 58620?

ZIP code 58620 (Amidon, ND) 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 Amidon, ND?

The median last spring frost (32 °F) near 58620 is May 12; after May 28 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Amidon station.

When is the first frost in Amidon, ND?

The median first fall frost near 58620 is September 29, giving a median frost-free growing season of 136 days.

When should I plant tomatoes in 58620?

Start tomato seeds indoors around Mar 17 – Mar 31 and set transplants outside around May 19 – Jun 2, one to three weeks after the median last frost.

How much rain and snow does 58620 get?

About 17.1 inches of precipitation a year and 48 inches of snowfall (NOAA 1991–2020 normals, Bowman station).

How hot do summers get in Amidon, ND?

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 58620 have?

The USDA soil survey maps Shambo at the center of ZIP 58620: loam, well drained, pH about 6.3 (slightly acidic).

Did spring come early in Amidon, ND in 2026?

Spring leaf-out near 58620 came on Apr 8 in 2026, 7 days earlier than the 1991–2020 average (Apr 15), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Amidon, ND?

Long-day onions: the longest day near 58620 is 15 h 49 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).

Did the zone for 58620 change?

Yes. The 2012 USDA map put 58620 in zone 4a; the 2023 map puts it in zone 4b. The newer map uses 1991–2020 data and more weather stations.