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

Planting zone for 57346 — Stephan, SD

ZIP code 57346 (Stephan, Hyde County) is in USDA zone 4b: the coldest winter night averages −25 to −20 °F. The median last spring frost is May 10 and the first fall frost September 29.

Where ZIP 57346 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 10

First frostSep 29

2012 zone4b

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 4b means →

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for Stephan, SD…

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 Stephan, SD

JanFebMarAprMayJunJulAugSepOctNovDec

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

Last spring frostMay 10median — 50% chance of a later frost

Safe for tender plantsMay 24only 10% chance of frost after

First fall frostSeptember 29median — 10% chance by Sep 16

Growing season140 daysfrost-free, median

A hard freeze (28 °F) usually ends around May 2 and returns around October 6.

From the NOAA station Stephan 2 Nw, SD — within 1 mile, elevation 1,805 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 57346

JanFebMarAprMayJunJulAugSepOctNovDec

PeasSow outdoors · Mar 29 – Apr 12

SpinachSow outdoors · Mar 29 – Apr 19

Broccoli, cabbageStart indoors · Mar 1 – Mar 15

Broccoli, cabbageTransplant · Apr 19 – May 3

Onion setsPlant outdoors · Apr 12 – Apr 26

PotatoesPlant outdoors · Apr 19 – May 3

LettuceSow outdoors · Apr 12 – Apr 26

Carrots, beetsSow outdoors · Apr 19 – May 3

TomatoesStart indoors · Mar 15 – Mar 29

TomatoesTransplant · May 17 – May 31

Peppers, eggplantStart indoors · Mar 1 – Mar 15

Peppers, eggplantTransplant · May 24 – Jun 7

BeansSow outdoors · May 17 – May 31

Sweet cornSow outdoors · May 17 – May 31

Cucumbers, squashSow outdoors · May 17 – May 31

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 10) 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 57346 came on Mar 25 — 18 days earlier than the 1991–2020 average (Apr 12).

average
Apr 122026
Mar 25

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 South Dakota

430 plants native to the lower 48 states, recorded in South 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 Stephan, SD.

Soil in Stephan, SD

The soil mapped at the center of ZIP 57346 is Promise — clay, well drained.

TextureClayholds water and nutrients; slow to drain and warm up

pH7.0neutral; most vegetables like 6.0–7.0

DrainageWell drainednatural drainage class

Organic matter4%moderate

Hydrologic groupDwater soaks in very slowly

Farmland classFarmland of statewide importanceUSDA classification

Map unit: Promise clay, 3 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 57346; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Stephan, SD

Summer high85 °Faverage high, July

Winter low5 °Faverage low, January

Hot days26days a year at 90 °F or more

Freezing nights179nights a year at 32 °F or less

Growing degree days2,558base 50 °F — the season’s usable heat

Longest day15 h 31 mindaylight on June 21

Shortest day8 h 51 mindaylight on December 21

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

Precipitation21.2 inper year, rain and melted snow

Snowfall37 inper year

Average high and low, by month

Precipitation by month inches · ❄ = snowfall

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Stephan 2 Nw, SD (within 1 mile); precipitation: Stephan 2 Nw, SD (within 1 mile). 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.

573394b

Fort Thompson, SD · 8 mi

575484b

Lower Brule, SD · 9 mi

575404b

Holabird, SD · 16 mi

573714b

Ree Heights, SD · 17 mi

573414b

Gann Valley, SD · 20 mi

Chamberlain, SD · 30 mi

South Dakota planting zones →

Questions about 57346

What planting zone is ZIP code 57346?

ZIP code 57346 (Stephan, SD) 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 Stephan, SD?

The median last spring frost (32 °F) near 57346 is May 10; after May 24 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Stephan 2 Nw station.

When is the first frost in Stephan, SD?

The median first fall frost near 57346 is September 29, giving a median frost-free growing season of 140 days.

When should I plant tomatoes in 57346?

Start tomato seeds indoors around Mar 15 – Mar 29 and set transplants outside around May 17 – May 31, one to three weeks after the median last frost.

How much rain and snow does 57346 get?

About 21.2 inches of precipitation a year and 37 inches of snowfall (NOAA 1991–2020 normals, Stephan 2 Nw station).

How hot do summers get in Stephan, SD?

The average high peaks at 85 °F in July, with about 26 days a year at 90 °F or more.

What kind of soil does 57346 have?

The USDA soil survey maps Promise at the center of ZIP 57346: clay, well drained, pH about 7.0 (neutral).

Did spring come early in Stephan, SD in 2026?

Spring leaf-out near 57346 came on Mar 25 in 2026, 18 days earlier than the 1991–2020 average (Apr 12), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Stephan, SD?

Long-day onions: the longest day near 57346 is 15 h 31 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).