Clay County, in South Dakota, sits in USDA hardiness zone 5a — room for a real mix of vegetables, fruit, and perennials matched to the local frost calendar.
Growers here do well with tomato, black hills spruce, potato, and rhubarb — with the usual caveat that any single yard's soil, sun, and drainage cast the deciding vote.
Grounded in USDA PHZM 2023 · Growable Ground suitability scoring · NOAA 1991–2020 Climate Normals
Clay County holds more than one microclimate.
Soils and elevations shift across Clay County, so your frost dates and drainage aren't the county average. Enter your address and we'll score 1,112 plants against your land's actual soil, sun, and frost.
We read public map data for this spot — soil, climate, flood, and parcel records. How we handle your address.
No card required · your full report in seconds
Quick Facts
USDA Zones
5a
Last Hard Freeze (28°F)
Apr 4
County normal — light frosts run a few weeks later
First Hard Freeze (28°F)
Oct 31
County normal — light frosts arrive a few weeks earlier
County Area
264K acres
Hardiness Zone Range
Zone maps are averages across Clay County. Your yard's slope, trees, and frost pockets shift what actually grows — see your land's exact reading.
Soil in Clay County
Across Clay County, the ground is predominantly Mollisols, where Egan, Luton, and Ethan are the most extensive named soil series. The soil is generally well drained with a silty clay loam surface. Topsoil pH runs about 6.7–7.5, neutral. Rainfall drains through hydrologic group C soils.
Soil order
Mollisols
Drainage
Well drained
Prime farmland
56%
Hydric soils
25%
Soil still varies lot by lot — soil types explained.
What Grows in Clay County
Plants matched to Clay County's USDA zones 5a — each links to its full growing profile.
Is it too late to plant in Clay County?
For most of the year, no — what changes is which crops still fit the days remaining. Cool-season crops can go in from around Mar 7; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near Apr 4 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Oct 31 — long-season crops need about 90 days of runway, quick greens only 30. There is slack in a calendar like this — late plantings, second rounds of favorites, and a fall bench that keeps beds working.
Growing Challenges in South Dakota
What an experienced grower plans around here — each one has a move.
Extreme cold and short growing season
Cold-proven varieties and a high tunnel turn a short prairie season into a reliable one — the northern-plains standard.
Low rainfall in western SD
West-river gardens run on drip and mulch — putting the water plan first makes the dry summers routine.
Wind exposure on the open prairie
A windbreak is the best structure you can plant on the prairie — even a shrub row shifts the microclimate.
For cultivar selection, pest pressure, and planting-time guidance specific to South Dakota, the SDSU Extension is the authoritative local source.
Safe to Grow Here?
What the federal record shows across Clay County — and how to grow with it.
We checked the federal record across Clay County — 207 documented sites across 5 of the 9 source types we track.
The most significant on record: 1 Toxics Release Inventory facility. Active industrial facilities reporting chemical releases to air, water, and land.
There's a meaningful federal record across Clay County — worth a look before you plant food, not a reason to hold back from growing. Proximity to a documented site is information, not a diagnosis of any one yard. A soil test before new food beds is the sensible precaution here, and the map shows exactly which sites sit where, so you can see what's actually near you.
Sources: EPA, USGS — 1.8M documented sites tracked nationwide across 9 federal source types.
Environmental Intelligence
Understanding what's nearby helps you make informed decisions about where and how to grow.
Total Sites
207
across Clay County
Risk Level
Elevated
Highest-severity
1 Toxics Release Inventory facility
Sources Checked
across Clay County
Severity Distribution
across Clay County
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around Clay County, Nitrate runs higher than the national average — 154 sites nearby. Knowing it is half the work — and it's nothing a thoughtful grower can't plan for.
Nitrate: Nitrate contamination primarily comes from agricultural fertilizer runoff and failing septic systems.
Test well water for nitrate if you rely on a private well for irrigation (EPA standard: 10 mg/L).
Check your specific parcel in Clay County
Get exact proximity distances to contamination sources for your specific parcel — plus soil, sun, drainage, and 1,112 plant recommendations.
Three things about your exact spot that zone averages miss:
We read public map data for this spot — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources analyzed in seconds
Your Specific Parcel Matters
Clay County Average
- ●USDA Zones 5a
- ●Generic soil type for the area
- ●State-average frost dates
YOUR Parcel
- ✓Your exact hardiness zone
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your parcel in Clay County
Pull a site-specific report for your exact address in Clay County, South Dakota — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your exact spot that zone averages miss:
We read public map data for this spot — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources analyzed in seconds
Key Growing Facts for Clay County, South Dakota
- USDA Hardiness Zones: 5a (USDA PHZM 2023)
- Last Hard Freeze (28°F): Apr 4 (county normal, NOAA 1991–2020 Climate Normals — light frosts can follow for a few weeks)
- First Hard Freeze (28°F): Oct 31 (county normal, NOAA 1991–2020 Climate Normals — light frosts can arrive a few weeks earlier)
- Days Between Hard Freezes: ~210 (county normal, NOAA 1991–2020 Climate Normals)
- County Land Area: 264K acres (US Census TIGER 2025)
Zone data: USDA ARS Plant Hardiness Zone Map 2023. Climate data: NOAA NCEI. County boundaries: US Census TIGER/Line 2025.
Frost dates here are the Clay County average. Low spots and tree cover move them by days on any one yard — see your exact frost windows.
Frequently Asked Questions
What hardiness zone is Clay County, South Dakota?
Clay County sits in USDA hardiness zone 5a, per the USDA Plant Hardiness Zone Map 2023. Zones reflect average annual extreme minimum temperatures from 1991–2020 weather data.
Is it too late to plant in Clay County?
For most of the year, no — what changes is which crops still fit the days remaining. Cool-season crops can go in from around Mar 7; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near Apr 4 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Oct 31 — long-season crops need about 90 days of runway, quick greens only 30. There is slack in a calendar like this — late plantings, second rounds of favorites, and a fall bench that keeps beds working.
When does frost risk typically end in Clay County?
The last hard freeze (28°F) in Clay County typically lands around Apr 4, per NOAA 1991–2020 climate normals — an earlier marker than the light-frost dates many planting charts quote. That marks the hard freeze, not the last light frost — light frosts can still bite for a few more weeks, so tender transplants usually wait another 2–3 weeks.
How long is the growing season in Clay County?
Measured between 28°F hard freezes, Clay County sees about 210 frost-free days — roughly Apr 4 through Oct 31, per NOAA 1991–2020 climate normals. Tender crops get a somewhat shorter practical window, since lighter frosts reach a few weeks past the hard-freeze dates on both ends.
What vegetables grow in Clay County?
Clay County's zone 5a supports a wide range — strong performers include Tomato, Black Hills Spruce, Potato, and Rhubarb. What actually takes on any one site comes down to its soil, sun, and drainage, and we score each plant against the real conditions at your address.
Which hardiness zone is Clay County, really?
Officially, Clay County sits in USDA zone 5a (USDA PHZM 2023) — but a zone is a 30-year average of winter's coldest night across an area, and it can't see any one yard. A south-facing slope, a tree line, or a low frost pocket can shift a single site by half a zone either way, which is why neighboring gardeners often quote different numbers. We read the conditions at your exact address — soil, sun, slope, and frost — and score 1,112 plants against what's actually there.
Is the soil safe to grow vegetables in Clay County?
The federal record around Clay County is a meaningful one — 207 documented sites — so a soil test before new food beds is a sensible precaution here, not a reason to hold back from growing. Remember that proximity to a documented site is information, not a diagnosis of any one yard; the contamination map shows exactly what sits where.
Just moved to Clay County — what should I know before planting?
Start with three facts. Clay County sits in USDA zone 5a, which sets what survives winter; the last 28°F hard freeze typically clears around Apr 4, with about 210 frost-free days to work with (NOAA 1991–2020 climate normals); and 207 documented sites sit on the federal record here, so a soil test before food beds is the smart first step. From there, matching plants to your actual soil and sun is the fun part.
Everything on this page is a Clay County average. Your yard writes its own version — we read soil, sun, drainage, and frost at your exact address. Try it for 14 days — no card required.
Will It Grow Here?
Zone fit is the first question — each answer below reads South Dakota's frost window, season length, and soil profile against the plant's real requirements.