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

Planting zone for 57223 — Castlewood, SD

ZIP code 57223 (Castlewood, Hamlin County) is in USDA zone 4a: the coldest winter night averages −30 to −25 °F. The median last spring frost is May 10 and the first fall frost September 27.

Where ZIP 57223 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 10
First frostSep 27
2012 zone4a

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 4a means →

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for Castlewood, 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 Castlewood, 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 23only 10% chance of frost after
First fall frostSeptember 27median — 10% chance by Sep 14
Growing season139 daysfrost-free, median

A hard freeze (28 °F) usually ends around May 1 and returns around October 4.

From the NOAA station Castlewood, SD — 2 miles away, elevation 1,686 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 57223

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 2 – Aug 16
GarlicPlant cloves · Sep 13 – Oct 18
Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (May 10) and first fall frost (Sep 27) 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 57223 came on Apr 12 — 7 days earlier than the 1991–2020 average (Apr 19).

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 South Dakota

384 plants native to the lower 48 states, recorded in South Dakota, and rated by the USDA to survive −30 °F or colder — the bottom of zone 4a. Each links to its USDA PLANTS profile.

Trees 21

American basswood100 ft · blooms late spring · low shade tolerance · to −46 °FAmerican elm120 ft · blooms early spring · medium shade tolerance · to −46 °Fbalsam poplar80 ft · blooms late spring · high shade tolerance · to −79 °Fblack locust60 ft · blooms spring · high shade tolerance · to −37 °Fblack maple100 ft · blooms late spring · low shade tolerance · to −47 °Fboxelder60 ft · blooms early spring · low shade tolerance · to −46 °F

Shrubs 62

alderleaf buckthorn3 ft · blooms late spring · low shade tolerance · to −33 °Falderleaf mountain mahogany15 ft · blooms late spring · medium shade tolerance · to −41 °FAmerican black currant3 ft · blooms early spring · to −46 °FAmerican hazelnut10 ft · blooms spring · medium shade tolerance · to −33 °FAmerican plum24 ft · blooms mid spring · high shade tolerance · to −38 °Fbeaked hazelnut15 ft · blooms early spring · low shade tolerance · to −47 °F

Wildflowers & perennials 165

alkali buttercup1 ft · blooms late spring · low shade tolerance · to −38 °Falpine bistort1 ft · blooms mid spring · high shade tolerance · to −38 °Falpine mountainsorrel1 ft · blooms mid summer · medium shade tolerance · to −43 °Falpine sweetvetch2 ft · blooms early summer · high shade tolerance · to −62 °FAmerican eelgrass1 ft · blooms mid summer · high shade tolerance · to −33 °FAmerican licorice4 ft · blooms late spring · medium shade tolerance · to −38 °F

Grasses 126

Alaska oniongrass3 ft · blooms mid spring · low shade tolerance · to −33 °Falkali cordgrass3 ft · blooms late summer · high shade tolerance · to −38 °Falkali sacaton3 ft · blooms mid summer · high shade tolerance · to −38 °Falpine timothy1.4 ft · blooms late spring · medium shade tolerance · to −43 °Farctic brome3 ft · blooms early summer · low shade tolerance · to −33 °Fawlfruit sedge4 ft · blooms mid spring · low shade tolerance · to −38 °F

Vines 4

American bittersweet15 ft · blooms spring · low shade tolerance · to −38 °Fdevil's darning needles15 ft · blooms mid summer · medium shade tolerance · to −38 °Friverbank grape45 ft · blooms late spring · medium shade tolerance · to −33 °Fwestern white clematis1 ft · blooms mid summer · medium shade tolerance · to −38 °F

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 Castlewood, SD.

Soil in Castlewood, SD

The soil mapped at the center of ZIP 57223 is Vienna — silt loam, well drained.

TextureSilt loama good balance for most vegetables
pH6.4slightly acidic; most vegetables like 6.0–7.0
DrainageWell drainednatural drainage class
Organic matter3%moderate
Hydrologic groupCwater soaks in slowly
Farmland classprime farmlandUSDA classification

Map unit: Vienna-Brookings complex, 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 57223; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Castlewood, SD

Summer high81 °Faverage high, July
Winter low2 °Faverage low, January
Hot days9days a year at 90 °F or more
Freezing nights187nights a year at 32 °F or less
Growing degree days2,157base 50 °F — the season’s usable heat
Longest day15 h 35 mindaylight on June 21
Shortest day8 h 48 mindaylight on December 21
Onions to growLong-daysummer days reach 15+ hours, enough for long-day varieties (intermediate types work too)
Precipitation24.8 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 20 °F, low 2 °F 20°2° JanFebruary: average high 26 °F, low 5 °F 26°5° FebMarch: average high 38 °F, low 18 °F 38°18° MarApril: average high 53 °F, low 30 °F 53°30° AprMay: average high 65 °F, low 43 °F 65°43° MayJune: average high 76 °F, low 54 °F 76°54° JunJuly: average high 81 °F, low 58 °F 81°58° JulAugust: average high 79 °F, low 56 °F 79°56° AugSeptember: average high 71 °F, low 46 °F 71°46° SepOctober: average high 56 °F, low 33 °F 56°33° OctNovember: average high 39 °F, low 20 °F 39°20° NovDecember: average high 25 °F, low 8 °F 25°8° Dec

Precipitation by month inches

0″1″2″3″4″January: 0.52 in precipitation 0.5 JanFebruary: 0.63 in precipitation 0.6 FebMarch: 1.18 in precipitation 1.2 MarApril: 2.06 in precipitation 2.1 AprMay: 3.87 in precipitation 3.9 MayJune: 3.98 in precipitation 4.0 JunJuly: 3.45 in precipitation 3.5 JulAugust: 2.82 in precipitation 2.8 AugSeptember: 3.06 in precipitation 3.1 SepOctober: 1.93 in precipitation 1.9 OctNovember: 0.76 in precipitation 0.8 NovDecember: 0.52 in precipitation 0.5 Dec

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

Nearby ZIP codes

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

572344b
Estelline, SD · 9 mi
572414b
Hayti, SD · 11 mi
572384b
Goodwin, SD · 13 mi
572484b
Lake Norden, SD · 13 mi
572454b
Kranzburg, SD · 13 mi
572264b
Clear Lake, SD · 14 mi
572014b
Watertown, SD · 16 mi
572204b
Bruce, SD · 18 mi

South Dakota planting zones →

Questions about 57223

What planting zone is ZIP code 57223?

ZIP code 57223 (Castlewood, SD) 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 Castlewood, SD?

The median last spring frost (32 °F) near 57223 is May 10; after May 23 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Castlewood station.

When is the first frost in Castlewood, SD?

The median first fall frost near 57223 is September 27, giving a median frost-free growing season of 139 days.

When should I plant tomatoes in 57223?

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 57223 get?

About 24.8 inches of precipitation a year (NOAA 1991–2020 normals, Castlewood station).

How hot do summers get in Castlewood, SD?

The average high peaks at 81 °F in July, with about 9 days a year at 90 °F or more.

What kind of soil does 57223 have?

The USDA soil survey maps Vienna at the center of ZIP 57223: silt loam, well drained, pH about 6.4 (slightly acidic).

Did spring come early in Castlewood, SD in 2026?

Spring leaf-out near 57223 came on Apr 12 in 2026, 7 days earlier than the 1991–2020 average (Apr 19), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Castlewood, SD?

Long-day onions: the longest day near 57223 is 15 h 35 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).