River Sioux, Iowa, sits in USDA hardiness zone 5a — a band that supports both cool-season staples and warm-season crops chosen to fit the local frost window.
Expect cabbage, cranberry, lavender, and collard greens to be strong candidates here; the deciding factors on any one parcel stay local — soil, sun, and drainage.
Even in River Sioux, 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 River Sioux 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 River Sioux — soil, climate, flood, and parcel records. How we handle your address.
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River Sioux — the short answer
River Sioux, Iowa: USDA zone 5a, about 188 days between hard freezes, across 244 acres of town.
- USDA zone
- 5a
- USDA PHZM 2023
- Last hard freeze (28°F)
- Apr 14
- NOAA 1991–2020 Climate Normals, 28°F — this town
- First hard freeze (28°F)
- Oct 19
- NOAA 1991–2020 Climate Normals, 28°F — this town
- Days between freezes
- ~188
- NOAA 1991–2020 Climate Normals, 28°F — this town
- Town area
- 244 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 River Sioux's average, not your lot's — a low corner or a tree line moves it. Against River Sioux's 188-day season, see what your own ground reads.
Soil varies lot by lot — soil types explained.
What this means for growing in River Sioux
Each reading below is measured for River Sioux itself — here is what it means for a garden here, and the move an experienced grower makes about it.
Season length
MeasuredRiver Sioux runs about 188 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
MeasuredRiver Sioux 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 River Sioux is in
River Sioux sits in the Western Corn Belt Plains — EPA Level III, inside the wider Great Plains. That is read at River Sioux's own centroid rather than borrowed from Harrison County.
What Grows in River Sioux
Every plant below cleared River Sioux's own zone 5a and its 188-day season. Each card opens that plant's Iowa profile. How we score.
Is it too late to plant in River Sioux?
Almost never — the real question is what to plant next. Cool-season crops can go in from around Mar 17; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near Apr 14 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Oct 19 — long-season crops need about 90 days of runway, quick greens only 30. As the window narrows, the plantings just get faster — fall brassicas, then greens, then garlic to finish.
What's on the federal record near River Sioux
Closest first, within ~10 miles of River Sioux. Listing isn't leaking, and distance isn't exposure.
- WOODLAND MINI STOREUnderground Storage Tanks · 0.7 mi
- STUCKEYS OF LITTLE SIOUXUnderground Storage Tanks · 1.4 mi
- 081N45W24DABD 34629 1972Little Sioux 1Nitrate · 1.4 mi
- SECONDARY ROAD DEPARTMENTUnderground Storage Tanks · 1.5 mi
- 21N 12E18DD (M-214)Nitrate · 2.8 mi
- 21N 12E07DC (M-202)Nitrate · 2.9 mi
- 081N44W18AADA 26513 1981IGS & USGS WC-23Nitrate · 3.1 mi
- 21N 11E 12DB (M-234)Nitrate · 3.7 mi
- BROWER CONSTRUCTION COBrownfields · 6.3 mi
- HARRISON COUNTYUnderground Storage Tanks · 6.5 mi
- 080N45W25DABD 1929Mondamin 1Nitrate · 6.5 mi
- 080N45W25DABD 1951Mondamin 2 SouthNitrate · 6.5 mi
6 more sites are on the record inside the same radius. See them on the map
Measured from River Sioux'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 River Sioux.
Sources Checked
within ~10 miles of River Sioux
Severity Distribution
within ~10 miles of River Sioux
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around River Sioux, Nitrate runs higher than the national average — 40 sites within ~10 miles of River Sioux. 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 River Sioux
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 River Sioux average
Your land is one point inside River Sioux
Everything above resolves to River Sioux as a whole — one PHZM band and one 28°F frost record, read across 244 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 town 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 River Sioux Average
River Sioux Average
- ●USDA Zones 5a, averaged across River Sioux
- ●One soil character for all of River Sioux
- ●Frost dates read at River Sioux's scale: Apr 14 to Oct 19
YOUR Parcel
- ✓Your exact zone, not River Sioux's 5a
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your specific parcel in River Sioux
Pull a site-specific report for your exact address in River Sioux, Iowa — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that River Sioux averages can't show:
We read public map data around River Sioux — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the River Sioux average
How we know this about River Sioux
The datasets: hardiness from the USDA ARS Plant Hardiness Zone Map 2023, read at this town’s own centroid; hard-freeze dates from NOAA 1991–2020 28°F normals at River Sioux’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 town grain anywhere on this page — there is no town-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 River Sioux
When does frost risk typically end in River Sioux?
The last hard freeze (28°F) in River Sioux typically lands around Apr 14, 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 5.
When is the first frost in River Sioux?
The first hard freeze (28°F) in River Sioux typically arrives around Oct 19, per NOAA 1991–2020 climate normals — the point tender summer crops finish. Lighter frosts run ahead of it, near Oct 5, so the watching starts about Sep 19 — about 188 days after the spring freeze cleared.
How long is the growing season in River Sioux?
Measured between 28°F hard freezes, River Sioux sees about 188 frost-free days — roughly Apr 14 through Oct 19, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer May 5 to Oct 5, about 153 days.
Is the soil safe to grow vegetables in River Sioux?
The federal record around River Sioux shows 63 documented sites, mostly Nitrate entries (40), the nearest Underground Storage Tanks record about 0.7 miles 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 River Sioux?
From about Sep 19 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 19 (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 19. Hardy greens and roots shrug off light frost and sweeten after it — leave them in.
Everything above is measured at River Sioux's scale — its 5a band and its 188-day season. Your yard writes its own version of River Sioux'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 River Sioux’s own scale
6 of the readings below were taken at River Sioux's own scale — its own ~188-day season between 28°F freezes, the 244 acres it covers and 63 documented sites around it; 4 are borrowed from a wider read, named and linked below.
Measured here
- River Sioux's own USDA hardiness band, zones 5aUSDA PHZM 2023
- River Sioux's own 28°F hard-freeze dates, about Apr 14 and Oct 19 and the ~188-day span between themNOAA 1991–2020 Climate Normals
- 63 documented contamination sites on the federal record near River Sioux, the closest Underground Storage Tanks record about 0.7 miles out from the town centreFederal environmental registers
- River Sioux's boundary and the 244 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 5a and a ~188-day seasonGrowable Ground crop-matching engine
- The ecoregion at River Sioux'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 River Sioux's 244 acres read through its county's SSURGO summaryfrom Harrison County
- Growing-degree days and winter chill — measured county-wide only, so the county page carries themfrom Harrison 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 Harrison County
What this page can’t tell you
- The soil pH, drainage, sun hours, and frost pockets on any one lot among River Sioux's 244 acreswhy one lot differs from the next →
- Which side of River Sioux you're on — a low spot frosts first and a south wall warms early, and one normal is being asked to speak for all 244 acresreading your own microclimate →
- How close that record sits to YOUR lot — the closest Underground Storage Tanks record about 0.7 miles 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 River Sioux-wide figureread your own land →
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