Rock Rapids, Iowa, sits in USDA hardiness zone 5a — a range where zone-matched perennials and frost-aware annual timing set what succeeds.
A short list that earns its place here — cabbage, cranberry, lavender, and collard greens — with any one site's soil, sun, and drainage making the final cut.
Even in Rock Rapids, 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 Rock Rapids 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 Rock Rapids — soil, climate, flood, and parcel records. How we handle your address.
No card required · your full report in seconds
Rock Rapids — the short answer
Rock Rapids, Iowa: USDA zone 5a, about 172 days between hard freezes, across 3K acres of city.
- USDA zone
- 5a
- USDA PHZM 2023
- Last hard freeze (28°F)
- Apr 23
- NOAA 1991–2020 Climate Normals, 28°F — this town
- First hard freeze (28°F)
- Oct 12
- NOAA 1991–2020 Climate Normals, 28°F — this town
- Days between freezes
- ~172
- NOAA 1991–2020 Climate Normals, 28°F — this town
- City area
- 3K 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 Rock Rapids's average, not your lot's — a low corner or a tree line moves it. Against Rock Rapids's 172-day season, see what your own ground reads.
Soil varies lot by lot — soil types explained.
What this means for growing in Rock Rapids
Each reading below is measured for Rock Rapids itself — here is what it means for a garden here, and the move an experienced grower makes about it.
Season length
MeasuredRock Rapids runs about 172 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
MeasuredRock Rapids 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 Rock Rapids is in
Rock Rapids sits in the Western Corn Belt Plains — EPA Level III, inside the wider Great Plains. That is read at Rock Rapids's own centroid rather than borrowed from Lyon County.
What Grows in Rock Rapids
Every plant below cleared Rock Rapids's own zone 5a and its 172-day season. Each card opens that plant's Iowa profile. How we score.
Is it too late to plant in Rock Rapids?
Too late for some crops, right on time for others — a growing season is a sequence, not a deadline. 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 12 — 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.
What's on the federal record near Rock Rapids
Closest first, within ~10 miles of Rock Rapids. Listing isn't leaking, and distance isn't exposure.
- 100N45W04BDDB 1975Rock Rapids 7Nitrate · 250 ft
- IDOT GARAGEUnderground Storage Tanks · 1000 ft
- LYON COUNTY SHERIFFUnderground Storage Tanks · 1000 ft
- ROCK RAPIDS UTILITIESUnderground Storage Tanks · 1200 ft
- LYON COUNTY ENGINEERUnderground Storage Tanks · 1200 ft
- DELL M GROOTERSUnderground Storage Tanks · 1300 ft
- MERRILL PIONEER COMMUNITY HOSPITALBrownfields · 1600 ft
- COOPERATIVE ENERGY COMPANYUnderground Storage Tanks · 1800 ft
- KOOLKER MOTORS INCUnderground Storage Tanks · 1900 ft
- MCCORMACK TRANSPORTATION CO INCUnderground Storage Tanks · 2000 ft
- BERGS 66 SERVICEUnderground Storage Tanks · 2100 ft
- DUSTYS AUTO BODYBrownfields · 2300 ft
6 more sites are on the record inside the same radius. See them on the map
Measured from Rock Rapids'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 Rock Rapids.
Total Sites
110
within ~10 miles of Rock Rapids
Risk Level
Moderate
Highest-severity
10 Toxics Release Inventory facilities
Sources Checked
within ~10 miles of Rock Rapids
Severity Distribution
within ~10 miles of Rock Rapids
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around Rock Rapids, two things run higher than the national average within ~10 miles of Rock Rapids — CAFO (5 sites) and Nitrate (46 sites). That's not a problem with your land — it's information about 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 Rock Rapids
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 Rock Rapids average
Your land is one point inside Rock Rapids
Everything above resolves to Rock Rapids as a whole — one PHZM band and one 28°F frost record, read across 3K 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 Rock Rapids Average
Rock Rapids Average
- ●USDA Zones 5a, averaged across Rock Rapids
- ●One soil character for all of Rock Rapids
- ●Frost dates read at Rock Rapids's scale: Apr 23 to Oct 12
YOUR Parcel
- ✓Your exact zone, not Rock Rapids's 5a
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your specific parcel in Rock Rapids
Pull a site-specific report for your exact address in Rock Rapids, Iowa — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Rock Rapids averages can't show:
We read public map data around Rock Rapids — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Rock Rapids average
How we know this about Rock Rapids
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 Rock Rapids’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 Rock Rapids
When does frost risk typically end in Rock Rapids?
The last hard freeze (28°F) in Rock Rapids 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.
When is the first frost in Rock Rapids?
The first hard freeze (28°F) in Rock Rapids typically arrives around Oct 12, per NOAA 1991–2020 climate normals — the point tender summer crops finish. Lighter frosts run ahead of it, near Sep 28, so the watching starts about Sep 12 — about 172 days after the spring freeze cleared.
How long is the growing season in Rock Rapids?
Measured between 28°F hard freezes, Rock Rapids sees about 172 frost-free days — roughly Apr 23 through Oct 12, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer May 14 to Sep 28, about 137 days.
Is the soil safe to grow vegetables in Rock Rapids?
The federal record around Rock Rapids shows 110 documented sites, mostly Nitrate entries (46), 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 Rock Rapids?
From about Sep 12 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 12 (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 12. Hardy greens and roots shrug off light frost and sweeten after it — leave them in.
Everything above is measured at Rock Rapids's scale — its 5a band and its 172-day season. Your yard writes its own version of Rock Rapids'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 Rock Rapids’s own scale
6 of the readings below were taken at Rock Rapids's own scale — its own ~172-day season between 28°F freezes, the 2,694 acres it covers and 110 documented sites around it; 4 are borrowed from a wider read, named and linked below.
Measured here
- Rock Rapids's own USDA hardiness band, zones 5aUSDA PHZM 2023
- Rock Rapids's own 28°F hard-freeze dates, about Apr 23 and Oct 12 and the ~172-day span between themNOAA 1991–2020 Climate Normals
- 110 documented contamination sites on the federal record near Rock Rapids, the closest Nitrate record under a tenth of a mile out from the town centreFederal environmental registers
- Rock Rapids's boundary and the 2,694 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 5a and a ~172-day seasonGrowable Ground crop-matching engine
- The ecoregion at Rock Rapids'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 Rock Rapids's 2,694 acres read through its county's SSURGO summaryfrom Lyon County
- Growing-degree days and winter chill — measured county-wide only, so the county page carries themfrom Lyon 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 Lyon County
What this page can’t tell you
- The soil pH, drainage, sun hours, and frost pockets on any one lot among Rock Rapids's 2,694 acreswhy one lot differs from the next →
- Which side of Rock Rapids you're on — a low spot frosts first and a south wall warms early, and one normal is being asked to speak for all 2,694 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 Rock Rapids-wide figureread your own land →
More in Iowa
Wider growing context
What grows across IowaRock Rapids sits outside our named growing regions, so Iowa as a whole is its closest context here.