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

Planting zone for 57231 — De Smet, SD

ZIP code 57231 (De Smet, Kingsbury County) is in USDA zone 4b: the coldest winter night averages −25 to −20 °F. The median last spring frost is May 5 and the first fall frost October 4.

Where ZIP 57231 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 5
First frostOct 4
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 De Smet, 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 De Smet, SD

JanFebMarAprMayJunJulAugSepOctNovDec
Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free
Last spring frostMay 5median — 50% chance of a later frost
Safe for tender plantsMay 20only 10% chance of frost after
First fall frostOctober 4median — 10% chance by Sep 23
Growing season151 daysfrost-free, median

A hard freeze (28 °F) usually ends around April 28 and returns around October 14.

From the NOAA station De Smet, SD — 2 miles away, elevation 1,706 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 57231

JanFebMarAprMayJunJulAugSepOctNovDec
PeasSow outdoors · Mar 24 – Apr 7
SpinachSow outdoors · Mar 24 – Apr 14
Broccoli, cabbageStart indoors · Feb 24 – Mar 10
Broccoli, cabbageTransplant · Apr 14 – Apr 28
Onion setsPlant outdoors · Apr 7 – Apr 21
PotatoesPlant outdoors · Apr 14 – Apr 28
LettuceSow outdoors · Apr 7 – Apr 21
Carrots, beetsSow outdoors · Apr 14 – Apr 28
TomatoesStart indoors · Mar 10 – Mar 24
TomatoesTransplant · May 12 – May 26
Peppers, eggplantStart indoors · Feb 24 – Mar 10
Peppers, eggplantTransplant · May 19 – Jun 2
BeansSow outdoors · May 12 – May 26
Sweet cornSow outdoors · May 12 – May 26
Cucumbers, squashSow outdoors · May 12 – May 26
Fall lettuce, spinachSow outdoors · Aug 9 – Aug 23
GarlicPlant cloves · Sep 20 – Oct 25
Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (May 5) and first fall frost (Oct 4) 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 57231 came on Apr 8 — 8 days earlier than the 1991–2020 average (Apr 16).

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 De Smet, SD

The soil mapped at the center of ZIP 57231 is Clarno — loam, well drained.

TextureLoama good balance for most vegetables
pH6.7neutral; most vegetables like 6.0–7.0
DrainageWell drainednatural drainage class
Organic matter3%moderate
Hydrologic groupBwater soaks in moderately
Farmland classFarmland of statewide importanceUSDA classification

Map unit: Clarno-Ethan-Bonilla loams, 1 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 57231; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in De Smet, SD

Summer high82 °Faverage high, July
Winter low5 °Faverage low, January
Hot days10days a year at 90 °F or more
Freezing nights165nights a year at 32 °F or less
Growing degree days2,461base 50 °F — the season’s usable heat
Longest day15 h 32 mindaylight on June 21
Shortest day8 h 50 mindaylight on December 21
Onions to growLong-daysummer days reach 15+ hours, enough for long-day varieties (intermediate types work too)
Precipitation25.9 inper year, rain and melted snow
Snowfall41 inper year; 91 days with snow on the ground

Average high and low, by month

−10°0°10°20°30°40°50°60°70°80°90°32 °FJanuary: average high 23 °F, low 5 °F 23°5° JanFebruary: average high 29 °F, low 9 °F 29°9° FebMarch: average high 41 °F, low 21 °F 41°21° MarApril: average high 55 °F, low 33 °F 55°33° AprMay: average high 67 °F, low 45 °F 67°45° MayJune: average high 77 °F, low 56 °F 77°56° JunJuly: average high 82 °F, low 61 °F 82°61° JulAugust: average high 79 °F, low 59 °F 79°59° AugSeptember: average high 72 °F, low 50 °F 72°50° SepOctober: average high 57 °F, low 36 °F 57°36° OctNovember: average high 41 °F, low 22 °F 41°22° NovDecember: average high 28 °F, low 10 °F 28°10° Dec

Precipitation by month inches · ❄ = snowfall

0″1″2″3″4″5″January: 0.60 in precipitation, 6.2 in snowfall 0.6❄6 JanFebruary: 0.88 in precipitation, 9.2 in snowfall 0.9❄9 FebMarch: 1.36 in precipitation, 6.9 in snowfall 1.4❄7 MarApril: 2.30 in precipitation, 4.8 in snowfall 2.3❄5 AprMay: 3.32 in precipitation 3.3 MayJune: 4.06 in precipitation 4.1 JunJuly: 3.88 in precipitation 3.9 JulAugust: 3.07 in precipitation 3.1 AugSeptember: 2.78 in precipitation 2.8 SepOctober: 1.98 in precipitation, 1.6 in snowfall 2.0❄2 OctNovember: 0.96 in precipitation, 5.4 in snowfall 1.0❄5 NovDecember: 0.74 in precipitation, 7.3 in snowfall 0.7❄7 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: De Smet, SD (2 mi away); precipitation: De Smet, SD (2 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

All 8 nearest ZIP codes share zone 4b.

572494b
Lake Preston, SD · 10 mi
573534b
Iroquois, SD · 12 mi
572334b
Erwin, SD · 13 mi
570514b
Oldham, SD · 16 mi
573234b
Carthage, SD · 16 mi
572214b
Bryant, SD · 18 mi
572784b
Willow Lake, SD · 19 mi
573864b
Yale, SD · 22 mi

South Dakota planting zones →

Questions about 57231

What planting zone is ZIP code 57231?

ZIP code 57231 (De Smet, 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 De Smet, SD?

The median last spring frost (32 °F) near 57231 is May 5; after May 20 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, De Smet station.

When is the first frost in De Smet, SD?

The median first fall frost near 57231 is October 4, giving a median frost-free growing season of 151 days.

When should I plant tomatoes in 57231?

Start tomato seeds indoors around Mar 10 – Mar 24 and set transplants outside around May 12 – May 26, one to three weeks after the median last frost.

How much rain and snow does 57231 get?

About 25.9 inches of precipitation a year and 41 inches of snowfall (NOAA 1991–2020 normals, De Smet station).

How hot do summers get in De Smet, SD?

The average high peaks at 82 °F in July, with about 10 days a year at 90 °F or more.

What kind of soil does 57231 have?

The USDA soil survey maps Clarno at the center of ZIP 57231: loam, well drained, pH about 6.7 (neutral).

Did spring come early in De Smet, SD in 2026?

Spring leaf-out near 57231 came on Apr 8 in 2026, 8 days earlier than the 1991–2020 average (Apr 16), according to the USA National Phenology Network Spring Index.

What kind of onions grow in De Smet, SD?

Long-day onions: the longest day near 57231 is 15 h 32 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).