Day County, in South Dakota, sits in USDA hardiness zone 4b — a range where zone-matched perennials and frost-aware annual timing set what succeeds.
Well-matched crops include cabbage, cranberry, turkish rocket, and collard greens, and the gap between "grows in the area" and "grows in your yard" is closed by soil, sun, and drainage.
Day County lies within the Coteau des Prairies / Glacial Lakes (Northeastern SD) — a regional growing area with its own character.
Grounded in USDA PHZM 2023 · Growable Ground suitability scoring · NOAA 1991–2020 Climate Normals
Day County holds more than one microclimate.
Soils and elevations shift across Day County, so your frost dates and drainage aren't the county average. Enter your address and we'll score 1,086 plants against your land's actual soil, sun, and frost.
We read public map data around Day County — soil, climate, flood, and parcel records. How we handle your address.
No card required · your full report in seconds
Day County — the short answer
Day County, South Dakota: USDA zone 4b, about 175 days between hard freezes, across 658K acres.
- USDA zone
- 4b
- USDA PHZM 2023
- Last hard freeze (28°F)
- Apr 23
- NOAA 1991–2020 Climate Normals, 28°F
- First hard freeze (28°F)
- Oct 15
- NOAA 1991–2020 Climate Normals, 28°F
- Days between freezes
- ~175
- NOAA 1991–2020 Climate Normals, 28°F
- County area
- 658K acres
- US Census TIGER/Line 2025
Every figure names the dataset it came from. Hard-freeze dates are county 28°F normals: light frosts run a few weeks past them, and tender transplants usually wait 2–3 weeks after the last hard freeze.
Hardiness Zone Range
Zone 4b is Day County's average, not your lot's — a low corner or a tree line moves it. Against Day County's 175-day season, see what your own ground reads.
Heat in Day County
Across a year, Day County accumulates about 2,220 growing degree days above 50°F, about 206 fewer than the middle South Dakota county — ahead of 14 of South Dakota’s 66 counties. Degree days are the heat a crop actually gets to work with — more of them is more room to ripen a long-season crop before the freeze closes the window.
Grounded in PRISM Climate Group, Oregon State University — 1991–2020 monthly normals
Soil in Day County
Across Day County, the ground is predominantly Mollisols, where Forman, Buse, and Aastad are the most extensive named soil series. The soil is generally well drained with a loam surface. Topsoil pH runs about 6.8–7.5, neutral. Rainfall drains through hydrologic group C soils.
Soil order
Mollisols
Drainage
Well drained
Prime farmland
42%
Hydric soils
18%
Soil still varies lot by lot — soil types explained.
How the ground varies across Day County
The USDA soil survey maps 65% of Day County as well drained — but another 32% drains differently: 13% very poorly drained, 6% somewhat excessively drained.
Forman is the most extensive named soil at 18% of mapped acres, then Buse (17%) and Aastad (9%).
Which of them your own lot sits on is a parcel question, not a county one. Check your address for the survey at your boundary.
What this means for growing in Day County
Each reading below is measured for Day County itself — here is what it means for a garden here, and the move an experienced grower makes about it.
Drainage
MeasuredThe dominant soils across Day County are well drained, in hydrologic group C — ground that drains quickly.
The upside is soil you can work early in spring and roots that never drown; the cost is that fast-draining ground dries out fast and leaches nutrients away before plants can use them.
Work in compost and mulch to hold moisture and feed, and water more often in short doses than deep and rarely.
USDA NRCS SSURGO
Surface pH
MeasuredTopsoil across Day County runs about pH 6.8–7.5, close to neutral.
This is the range most vegetables prefer — one correction you probably do not have to make, which is genuinely good news for a new bed.
Keep it there with compost rather than lime or sulfur, and only amend if your own soil test says otherwise.
USDA NRCS SSURGO
Wet ground
MeasuredAbout 18% of Day County is mapped as hydric — wetland — soil.
If your lot falls in one of those pockets, a standard in-ground bed will fight waterlogging all season, and roots that need air will struggle.
Check how your own ground drains before you dig; raised beds or moisture-loving plantings turn a wet corner from a problem into a niche.
USDA NRCS SSURGO
Season length
MeasuredDay County runs about 175 days between hard freezes — a moderate growing season.
There is room for the full run of cool-season crops plus a warm-season main crop, but the calendar is tight enough that a late spring or early fall frost still decides how much finishes.
Time warm-season transplants to your last hard freeze, and a few weeks of season extension turns a near-miss harvest into a sure one.
NOAA 1991–2020 Climate Normals
The kind of country Day County is in
Day County sits in the Northern Glaciated Plains — EPA Level III, inside the wider Great Plains. One consistent ecological setting across the whole county.
What Grows in Day County
We scored all 1,086 plants against Day County's own USDA zone 4b and its own 175-day season between hard freezes, using the same matching engine that runs a full parcel report. These cleared both. Sun, soil pH and drainage vary lot by lot — those are the parcel questions below. Each card opens that plant's South Dakota profile.
Is it too late to plant in Day 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 26; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near Apr 23 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Oct 15 — long-season crops need about 90 days of runway, quick greens only 30. Even past midsummer there is room for a true fall garden here, and garlic planted near the close carries the momentum into next year.
Documented around Day County
- monarch butterfly1 documented records
Sighting records, so they follow observers as much as insects.
What gets applied to farmland in Day County
USGS estimates 287,000 lb of Glyphosate on Day County farmland in 2019, its largest by weight, ahead of Metolachlor & Metolachlor-s (104,301 lb) and Metolachlor-s (97,017 lb).
Farmland across the whole county, not any one lot. Check your address for the site-by-site record.
Safe to Grow Here?
What the federal record shows across Day County — and how to grow with it.
We checked the federal record across Day County — 284 documented sites across 4 of the 9 source types we track.
The most significant on record: 2 Toxics Release Inventory facilities. Active industrial facilities reporting chemical releases to air, water, and land.
There's a meaningful federal record across Day 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.
What's on the federal record near Day County
Closest first, across Day County. Listing isn't leaking, and distance isn't exposure.
- 122N56W27CCDNitrate · 1.9 mi
- SD DEPT OF TRANSPORTATIONUnderground Storage Tanks · 2.0 mi
- 122N56W27BDDNitrate · 2.0 mi
- 122N56W34BDACNitrate · 2.3 mi
- 122N56W27AADC2Nitrate · 2.4 mi
- 122N56W27AADCNitrate · 2.4 mi
- DAY COUNTY EQUIP. INCUnderground Storage Tanks · 2.4 mi
- ESCO MANUFACTURING, INC.Brownfields · 2.8 mi
- DAKOTA FIBERGLASS INCToxics Release Inventory · 2.8 mi
- MEREEN-JOHNSON MACHINE COToxics Release Inventory · 2.9 mi
- MEREEN-JOHNSON MACHINE COBrownfields · 2.9 mi
- POWDERTECH CORPORATIONBrownfields · 2.9 mi
6 more sites are on the record inside the same radius. See them on the map
Measured from Day County's center, not your beds. Run your own address for what's upwind of you specifically.
Environmental Intelligence
The counts behind that headline — every source type on the record near Day County.
Total Sites
284
across Day County
Risk Level
Elevated
Highest-severity
2 Toxics Release Inventory facilities
Sources Checked
across Day County
Severity Distribution
across Day County
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around Day County, Nitrate runs higher than the national average — 224 sites across Day County. 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 Day County
Get exact proximity distances to contamination sources for your specific parcel — plus soil, sun, drainage, and 1,086 plant recommendations.
25+ data sources read at your address, not the Day County average
Your land is one point inside Day County
Everything above resolves to Day County as a whole — one PHZM band and one county frost record, read across 658K acres. Your parcel is one point inside that footprint. Slope, tree cover, a low spot that pools cold air, and what is in the soil are all resolved at the address, and none of them are visible at county scale. That is the honest boundary of this page, and the reason the next step is a reading of your own ground rather than a better county average.
Your Lot vs the Day County Average
Day County Average
- ●USDA Zones 4b, averaged across Day County
- ●One soil character for all of Day County
- ●Frost dates read at Day County's scale: Apr 23 to Oct 15
YOUR Parcel
- ✓Your exact zone, not Day County's 4b
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your parcel in Day County
Pull a site-specific report for your exact address in Day County, South Dakota — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Day County averages can't show:
We read public map data around Day County — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Day County average
How we know this about Day County
The datasets: hardiness from the USDA ARS Plant Hardiness Zone Map 2023, read at county grain; hard-freeze dates from NOAA 1991–2020 28°F normals at this county’s own record where one resolves, and the labelled statewide window where none does; soils from the USDA NRCS SSURGO survey, area-weighted across the county’s own map units; boundaries and acreage from US Census TIGER/Line 2025; the contamination and pesticide records from the federal sources named in their beats above. Where Day County carries no record of its own, the figure is inherited and labelled — the resolution ledger below names each.
Common questions about Day County
When does frost risk typically end in Day County?
The last hard freeze (28°F) in Day County typically lands around Apr 23, per NOAA 1991–2020 climate normals — earlier than the light-frost dates most charts quote. That marks the hard freeze, not the last light frost — lighter frosts keep biting past it, which is why tender transplants here wait until about May 14.
How long is the growing season in Day County?
Measured between 28°F hard freezes, Day County sees about 175 frost-free days — roughly Apr 23 through Oct 15, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer May 14 to Oct 1, about 140 days.
Is the soil safe to grow vegetables in Day County?
The federal record around Day County is a meaningful one — 284 documented sites, mostly Nitrate entries (224), the nearest Nitrate record about 1.9 miles out — 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.
Everything above is measured at Day County's scale — its 4b band and its 175-day season. Your yard writes its own version of Day County's numbers: 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.
What this page reads at Day County’s own scale
9 of the readings below were taken at Day County's own scale — its own ~175-day span between 28°F freezes, the 3 most extensive soil series mapped here and 284 documented sites inside its boundary; one is borrowed from a wider read, named and linked below.
Measured here
- Day County's own USDA hardiness band, zones 4bUSDA PHZM 2023
- Day County's own 28°F hard-freeze dates and its ~175-day span between themNOAA 1991–2020 Climate Normals
- The soil order, drainage, surface pH, and the 3 most extensive named soil series mapped in Day CountyUSDA NRCS SSURGO
- 284 documented contamination sites inside the county boundary, distance-sorted from its center — the closest Nitrate record about 1.9 miles outFederal environmental registers
- Day County's boundary and the 658,233 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 4b and a ~175-day seasonGrowable Ground crop-matching engine
- Day County sitting wholly inside the Northern Glaciated PlainsUS EPA Level III Ecoregions
- Open occurrence records documented in Day County for a tracked speciesGBIF derived datasets (CC0 / CC BY 4.0)
- Which agricultural compounds go onto Day County farmland, and roughly how muchUSGS NAWQA EPest county estimates
Inherited from a wider read
- The growing challenges every South Dakota grower plans around — written at state scale, so they stay on the state guidefrom South Dakota
What this page can’t tell you
- How the season shifts across Day County — the ~175 days above is one reading at its centre; the 12 towns below each carry their owntowns in this county →
- The soil pH, drainage, sun hours, and frost pockets on any one lot among Day County's 658,233 acreswhy one lot differs from the next →
- Which of those 284 documented sites actually reaches your soil — that needs your address, the wind, and the groundwater directionhow we read the record →
- Where cold air settles, which slopes face the sun, and which way the wind runs on your own ground — none of it survives being averaged over Day Countyread your own land →