Swea City, Iowa, sits in USDA hardiness zone 5a — a zone band wide enough that plant choice, not possibility, is the interesting question.
On paper, cabbage, cranberry, lavender, and collard greens all suit these conditions — on the ground, soil, sun, and drainage make the final call.
Even in Swea City, no two yards are alike.
A low spot, a south-facing slope, or a stand of trees moves the frost date and sun across a single Swea City lot. 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 Swea City — soil, climate, flood, and parcel records. How we handle your address.
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Swea City — the short answer
Swea City, Iowa: USDA zone 5a, about 183 days between hard freezes, across 491 acres of city.
- USDA zone
- 5a
- USDA PHZM 2023
- Last hard freeze (28°F)
- Apr 17
- NOAA 1991–2020 Climate Normals, 28°F — this town
- First hard freeze (28°F)
- Oct 17
- NOAA 1991–2020 Climate Normals, 28°F — this town
- Days between freezes
- ~183
- NOAA 1991–2020 Climate Normals, 28°F — this town
- City area
- 491 acres
- US Census TIGER/Line 2025
Every figure names the dataset it came from. Hard-freeze dates are this town’s own 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 5a is Swea City's average, not your lot's — a low corner or a tree line moves it. Against Swea City's 183-day season, see what your own ground reads.
Soil varies lot by lot — soil types explained.
What this means for growing in Swea City
Each reading below is measured for Swea City itself — here is what it means for a garden here, and the move an experienced grower makes about it.
Season length
MeasuredSwea City runs about 183 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
Winter hardiness
MeasuredSwea City sits in USDA hardiness zone 5a.
The zone sets which perennials, shrubs, and fruit trees live through an average winter here — a plant rated for a colder zone is a safe bet, one rated warmer needs winter protection or gets treated as an annual.
Match perennials and fruit to the zone before you buy, so nothing you plant is a gamble against the cold.
USDA PHZM 2023
The kind of country Swea City is in
Swea City sits in the Western Corn Belt Plains — EPA Level III, inside the wider Great Plains. That is read at Swea City's own centroid rather than borrowed from Kossuth County.
What Grows in Swea City
Every plant below cleared Swea City's own zone 5a and its 183-day season. Each card opens that plant's Iowa profile. How we score.
Is it too late to plant in Swea City?
Usually not — gardeners here simply switch what goes in the ground as the season moves. Cool-season crops can go in from around Mar 20; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near Apr 17 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Oct 17 — long-season crops need about 90 days of runway, quick greens only 30. Late in the year the fall bench takes over — quick greens, radishes, and garlic that repays you next summer.
What's on the federal record near Swea City
Closest first, within ~10 miles of Swea City. Listing isn't leaking, and distance isn't exposure.
- 099N29W19AAB 1935Swea City 2Nitrate · 450 ft
- GERLED SHOPUnderground Storage Tanks · 500 ft
- KOSSUTH COUNTY SHEDUnderground Storage Tanks · 500 ft
- NORTH SENTRAL KOSSUTH HIGH SCHOOLBrownfields · 550 ft
- KUM & GO #245Underground Storage Tanks · 600 ft
- CENEXUnderground Storage Tanks · 650 ft
- BOB BOLAND FORDUnderground Storage Tanks · 650 ft
- BRAND FX BODY COMPANY - SWEA CITYBrownfields · 750 ft
- BRAND FX BODY COMPANY - SWEA CITYToxics Release Inventory · 750 ft
- 099N29W19AABD 02217 1945Swea City 1Nitrate · 800 ft
- LOOFT''S 66 SERVICEUnderground Storage Tanks · 850 ft
- BRAND FX LLCBrownfields · 1100 ft
6 more sites are on the record inside the same radius. See them on the map
Measured from Swea City'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 Swea City.
Total Sites
82
within ~10 miles of Swea City
Risk Level
Moderate
Highest-severity
4 Toxics Release Inventory facilities
Sources Checked
within ~10 miles of Swea City
Severity Distribution
within ~10 miles of Swea City
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around Swea City, two things run higher than the national average within ~10 miles of Swea City — CAFO (4 sites) and Nitrate (28 sites). It's not cause for alarm — it's worth knowing, and there's a sensible way to grow around it.
CAFO: CAFOs pose a different contamination profile than chemical sources.
Nitrate: Nitrate contamination primarily comes from agricultural fertilizer runoff and failing septic systems.
Wash all produce consumed raw thoroughly, especially leafy greens grown near CAFOs.
Test well water for nitrate if you rely on a private well for irrigation (EPA standard: 10 mg/L).
Check your specific parcel in Swea City
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 Swea City average
Your land is one point inside Swea City
Everything above resolves to Swea City as a whole — one PHZM band and one 28°F frost record, read across 491 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 city 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 local average.
Your Lot vs the Swea City Average
Swea City Average
- ●USDA Zones 5a, averaged across Swea City
- ●One soil character for all of Swea City
- ●Frost dates read at Swea City's scale: Apr 17 to Oct 17
YOUR Parcel
- ✓Your exact zone, not Swea City's 5a
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your specific parcel in Swea City
Pull a site-specific report for your exact address in Swea City, Iowa — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Swea City averages can't show:
We read public map data around Swea City — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Swea City average
How we know this about Swea City
The datasets: hardiness from the USDA ARS Plant Hardiness Zone Map 2023, read at this city’s own centroid; hard-freeze dates from NOAA 1991–2020 28°F normals at Swea City’s own record; boundaries and acreage from US Census TIGER/Line 2025; the contamination records from the federal sources named in their beats above. Soil is not read at city grain anywhere on this page — there is no city-resolution survey in our data, which is why you will find no soil grid here rather than a statewide one wearing a local label. The resolution ledger below names every figure this page inherited.
Common questions about Swea City
When does frost risk typically end in Swea City?
The last hard freeze (28°F) in Swea City typically lands around Apr 17, 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 8.
When is the first frost in Swea City?
The first hard freeze (28°F) in Swea City typically arrives around Oct 17, per NOAA 1991–2020 climate normals — the point tender summer crops finish. Lighter frosts run ahead of it, near Oct 3, so the watching starts about Sep 17 — about 183 days after the spring freeze cleared.
How long is the growing season in Swea City?
Measured between 28°F hard freezes, Swea City sees about 183 frost-free days — roughly Apr 17 through Oct 17, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer May 8 to Oct 3, about 148 days.
Is the soil safe to grow vegetables in Swea City?
The federal record around Swea City shows 82 documented sites, mostly Underground Storage Tanks entries (32), the nearest Nitrate record under a tenth of a mile out — a typical footprint for a growing area, and proximity to a documented site is information, not a diagnosis of any one yard. It's worth seeing which recorded sites sit closest to where you grow, and testing the soil before new food beds near any of them.
How do I protect my plants from frost in Swea City?
From about Sep 17 the job here turns from planting to protecting — the last start even a 30-day crop can finish. As the season closes around the first 28°F hard freeze near Oct 17 (NOAA 1991–2020 climate normals), three moves buy time: row cover or an old sheet over tender plants on still, clear nights; water the soil the afternoon before a freeze, so it holds warmth overnight; and harvest tomatoes, peppers and basil before Oct 17. Hardy greens and roots shrug off light frost and sweeten after it — leave them in.
Everything above is measured at Swea City's scale — its 5a band and its 183-day season. Your yard writes its own version of Swea City's numbers: we read soil, sun, drainage and frost at your exact address. Try it for 14 days — no card required.
What this page reads at Swea City’s own scale
6 of the readings below were taken at Swea City's own scale — its own ~183-day season between 28°F freezes, the 491 acres it covers and 82 documented sites around it; 4 are borrowed from a wider read, named and linked below.
Measured here
- Swea City's own USDA hardiness band, zones 5aUSDA PHZM 2023
- Swea City's own 28°F hard-freeze dates, about Apr 17 and Oct 17 and the ~183-day span between themNOAA 1991–2020 Climate Normals
- 82 documented contamination sites on the federal record near Swea City, the closest Nitrate record under a tenth of a mile out from the town centreFederal environmental registers
- Swea City's boundary and the 491 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 5a and a ~183-day seasonGrowable Ground crop-matching engine
- The ecoregion at Swea City's own centroid, the Western Corn Belt PlainsUS EPA Level III Ecoregions
Inherited from a wider read
- Soil character — no town-scale survey exists, so Swea City's 491 acres read through its county's SSURGO summaryfrom Kossuth County
- Growing-degree days and winter chill — measured county-wide only, so the county page carries themfrom Kossuth County
- The growing challenges every Iowa grower plans around — written at state scale, so they stay on the state guidefrom Iowa
- Butterfly and beetle records, and the farmland pesticide estimate — all published county-widefrom Kossuth County
What this page can’t tell you
- The soil pH, drainage, sun hours, and frost pockets on any one lot among Swea City's 491 acreswhy one lot differs from the next →
- Which side of Swea City you're on — a low spot frosts first and a south wall warms early, and one normal is being asked to speak for all 491 acresreading your own microclimate →
- How close that record sits to YOUR lot — the closest Nitrate record under a tenth of a mile out, measured from the town centrehow we read the record →
- Where cold air settles, which slopes face the sun, and which way the wind runs on your own ground — measured at your address, and averaged away by any Swea City-wide figureread your own land →
More in Iowa
Wider growing context
What grows across IowaSwea City sits outside our named growing regions, so Iowa as a whole is its closest context here.