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

Planting zone for 57650 — Ralph, SD

ZIP code 57650 (Ralph, Harding County) is in USDA zone 4b: the coldest winter night averages −25 to −20 °F. The median last spring frost is May 18 and the first fall frost September 23.

Where ZIP 57650 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 18
First frostSep 23
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 Ralph, 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 Ralph, SD

JanFebMarAprMayJunJulAugSepOctNovDec
Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free
Last spring frostMay 18median — 50% chance of a later frost
Safe for tender plantsMay 31only 10% chance of frost after
First fall frostSeptember 23median — 10% chance by Sep 8
Growing season126 daysfrost-free, median

A hard freeze (28 °F) usually ends around May 8 and returns around October 1.

From the NOAA station Ralph 1 N, SD — 4 miles away, elevation 2,789 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 57650

JanFebMarAprMayJunJulAugSepOctNovDec
PeasSow outdoors · Apr 6 – Apr 20
SpinachSow outdoors · Apr 6 – Apr 27
Broccoli, cabbageStart indoors · Mar 9 – Mar 23
Broccoli, cabbageTransplant · Apr 27 – May 11
Onion setsPlant outdoors · Apr 20 – May 4
PotatoesPlant outdoors · Apr 27 – May 11
LettuceSow outdoors · Apr 20 – May 4
Carrots, beetsSow outdoors · Apr 27 – May 11
TomatoesStart indoors · Mar 23 – Apr 6
TomatoesTransplant · May 25 – Jun 8
Peppers, eggplantStart indoors · Mar 9 – Mar 23
Peppers, eggplantTransplant · Jun 1 – Jun 15
BeansSow outdoors · May 25 – Jun 8
Sweet cornSow outdoors · May 25 – Jun 8
Cucumbers, squashSow outdoors · May 25 – Jun 8
Fall lettuce, spinachSow outdoors · Jul 29 – Aug 12
GarlicPlant cloves · Sep 9 – Oct 14
Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (May 18) and first fall frost (Sep 23) 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 57650 came on Mar 31 — 15 days earlier than the 1991–2020 average (Apr 15).

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.

Trees 23

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 °Fblack walnut100 ft · blooms late spring · high shade tolerance · to −28 °F

Shrubs 65

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 191

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 138

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 5

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 °FVirginia creeper1 ft · blooms late spring · medium shade tolerance · to −28 °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 Ralph, SD.

Soil in Ralph, SD

The soil mapped at the center of ZIP 57650 is Amor — loam, well drained.

TextureLoama good balance for most vegetables
pH7.0neutral; most vegetables like 6.0–7.0
DrainageWell drainednatural drainage class
Organic matter4.5%moderate
Hydrologic groupCwater soaks in slowly
Farmland classNot prime farmlandUSDA classification

Map unit: Amor-Werner loams, 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 57650; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Ralph, SD

Summer high86 °Faverage high, July
Winter low7 °Faverage low, January
Hot days25days a year at 90 °F or more
Freezing nights193nights a year at 32 °F or less
Growing degree days2,238base 50 °F — the season’s usable heat
Longest day15 h 44 mindaylight on June 21
Shortest day8 h 40 mindaylight on December 21
Onions to growLong-daysummer days reach 15+ hours, enough for long-day varieties (intermediate types work too)
Precipitation16.2 inper year, rain and melted snow

Average high and low, by month

0°10°20°30°40°50°60°70°80°90°100°32 °FJanuary: average high 30 °F, low 7 °F 30°7° JanFebruary: average high 33 °F, low 10 °F 33°10° FebMarch: average high 45 °F, low 20 °F 45°20° MarApril: average high 57 °F, low 29 °F 57°29° AprMay: average high 68 °F, low 40 °F 68°40° MayJune: average high 77 °F, low 50 °F 77°50° JunJuly: average high 86 °F, low 56 °F 86°56° JulAugust: average high 86 °F, low 54 °F 86°54° AugSeptember: average high 76 °F, low 44 °F 76°44° SepOctober: average high 59 °F, low 31 °F 59°31° OctNovember: average high 43 °F, low 20 °F 43°20° NovDecember: average high 33 °F, low 10 °F 33°10° Dec

Precipitation by month inches

0″1″2″3″4″January: 0.49 in precipitation 0.5 JanFebruary: 0.71 in precipitation 0.7 FebMarch: 0.66 in precipitation 0.7 MarApril: 1.33 in precipitation 1.3 AprMay: 2.74 in precipitation 2.7 MayJune: 3.24 in precipitation 3.2 JunJuly: 2.22 in precipitation 2.2 JulAugust: 1.39 in precipitation 1.4 AugSeptember: 1.18 in precipitation 1.2 SepOctober: 1.19 in precipitation 1.2 OctNovember: 0.52 in precipitation 0.5 NovDecember: 0.52 in precipitation 0.5 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Ralph 1 N, SD (4 mi away); precipitation: Ralph 1 N, SD (4 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

All 8 nearest ZIP codes share zone 4b.

577554b
Ludlow, SD · 15 mi
576404b
Lodgepole, SD · 16 mi
586534b
Scranton, ND · 19 mi
586494b
Reeder, ND · 22 mi
576514b
Reva, SD · 24 mi
586394b
Hettinger, ND · 25 mi
576494b
Prairie City, SD · 25 mi
586234b
Bowman, ND · 29 mi

South Dakota planting zones →

Questions about 57650

What planting zone is ZIP code 57650?

ZIP code 57650 (Ralph, 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 Ralph, SD?

The median last spring frost (32 °F) near 57650 is May 18; after May 31 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Ralph 1 N station.

When is the first frost in Ralph, SD?

The median first fall frost near 57650 is September 23, giving a median frost-free growing season of 126 days.

When should I plant tomatoes in 57650?

Start tomato seeds indoors around Mar 23 – Apr 6 and set transplants outside around May 25 – Jun 8, one to three weeks after the median last frost.

How much rain and snow does 57650 get?

About 16.2 inches of precipitation a year (NOAA 1991–2020 normals, Ralph 1 N station).

How hot do summers get in Ralph, SD?

The average high peaks at 86 °F in July, with about 25 days a year at 90 °F or more.

What kind of soil does 57650 have?

The USDA soil survey maps Amor at the center of ZIP 57650: loam, well drained, pH about 7.0 (neutral).

Did spring come early in Ralph, SD in 2026?

Spring leaf-out near 57650 came on Mar 31 in 2026, 15 days earlier than the 1991–2020 average (Apr 15), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Ralph, SD?

Long-day onions: the longest day near 57650 is 15 h 44 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).

Did the zone for 57650 change?

Yes. The 2012 USDA map put 57650 in zone 4a; the 2023 map puts it in zone 4b. The newer map uses 1991–2020 data and more weather stations.