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

Planting zone for 57445 — Groton, SD

ZIP code 57445 (Groton, Brown County) is in USDA zone 4a: the coldest winter night averages −30 to −25 °F. The median last spring frost is May 6 and the first fall frost October 4.

Where ZIP 57445 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 6

First frostOct 4

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 Groton, 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 Groton, SD

JanFebMarAprMayJunJulAugSepOctNovDec

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

Last spring frostMay 6median — 50% chance of a later frost

Safe for tender plantsMay 21only 10% chance of frost after

First fall frostOctober 4median — 10% chance by Sep 21

Growing season150 daysfrost-free, median

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

From the NOAA station Andover #2, SD — 11 miles away, elevation 1,480 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 57445

JanFebMarAprMayJunJulAugSepOctNovDec

PeasSow outdoors · Mar 25 – Apr 8

SpinachSow outdoors · Mar 25 – Apr 15

Broccoli, cabbageStart indoors · Feb 25 – Mar 11

Broccoli, cabbageTransplant · Apr 15 – Apr 29

Onion setsPlant outdoors · Apr 8 – Apr 22

PotatoesPlant outdoors · Apr 15 – Apr 29

LettuceSow outdoors · Apr 8 – Apr 22

Carrots, beetsSow outdoors · Apr 15 – Apr 29

TomatoesStart indoors · Mar 11 – Mar 25

TomatoesTransplant · May 13 – May 27

Peppers, eggplantStart indoors · Feb 25 – Mar 11

Peppers, eggplantTransplant · May 20 – Jun 3

BeansSow outdoors · May 13 – May 27

Sweet cornSow outdoors · May 13 – May 27

Cucumbers, squashSow outdoors · May 13 – May 27

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 6) 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 57445 came on Apr 16 — about the same time as the 1991–2020 average (Apr 18).

average
Apr 182026
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 Groton, SD

The soil mapped at the center of ZIP 57445 is Beotia — silt loam, well drained.

TextureSilt loama good balance for most vegetables

pH7.0neutral; most vegetables like 6.0–7.0

DrainageWell drainednatural drainage class

Organic matter6%high

Hydrologic groupBwater soaks in moderately

Farmland classprime farmlandUSDA classification

Map unit: Beotia silt loam, 0 to 2 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 57445; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Groton, SD

Summer high82 °Faverage high, July

Winter low5 °Faverage low, January

Hot days11days a year at 90 °F or more

Freezing nights165nights a year at 32 °F or less

Growing degree days2,564base 50 °F — the season’s usable heat

Longest day15 h 41 mindaylight on June 21

Shortest day8 h 42 mindaylight on December 21

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

Precipitation22.6 inper year, rain and melted snow

Snowfall32 inper year

Average high and low, by month

Precipitation by month inches · ❄ = snowfall

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Andover #2, SD (11 mi away); precipitation: Groton, SD (2 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.

Stratford, SD · 14 mi

574334a

Columbia, SD · 16 mi

574324a

Claremont, SD · 16 mi

574494a

Houghton, SD · 18 mi

South Dakota planting zones →

Questions about 57445

What planting zone is ZIP code 57445?

ZIP code 57445 (Groton, 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 Groton, SD?

The median last spring frost (32 °F) near 57445 is May 6; after May 21 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Andover #2 station.

When is the first frost in Groton, SD?

The median first fall frost near 57445 is October 4, giving a median frost-free growing season of 150 days.

When should I plant tomatoes in 57445?

Start tomato seeds indoors around Mar 11 – Mar 25 and set transplants outside around May 13 – May 27, one to three weeks after the median last frost.

How much rain and snow does 57445 get?

About 22.6 inches of precipitation a year and 32 inches of snowfall (NOAA 1991–2020 normals, Groton station).

How hot do summers get in Groton, SD?

The average high peaks at 82 °F in July, with about 11 days a year at 90 °F or more.

What kind of soil does 57445 have?

The USDA soil survey maps Beotia at the center of ZIP 57445: silt loam, well drained, pH about 7.0 (neutral).

Did spring come early in Groton, SD in 2026?

Spring leaf-out near 57445 came on Apr 16 in 2026, about the same as the 1991–2020 average (Apr 18), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Groton, SD?

Long-day onions: the longest day near 57445 is 15 h 41 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).