Clear Lake, 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.
Crops well matched to these conditions include cabbage, cranberry, lavender, and collard greens — though what thrives on any one site still turns on its specific soil, sun, and drainage.
Even in Clear Lake, 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 Clear Lake 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 Clear Lake — soil, climate, flood, and parcel records. How we handle your address.
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Clear Lake — the short answer
Clear Lake, Iowa: USDA zone 5a, about 175 days between hard freezes, across 7K acres of city.
- USDA zone
- 5a
- USDA PHZM 2023
- Last hard freeze (28°F)
- Apr 19
- NOAA 1991–2020 Climate Normals, 28°F — this town
- First hard freeze (28°F)
- Oct 11
- NOAA 1991–2020 Climate Normals, 28°F — this town
- Days between freezes
- ~175
- NOAA 1991–2020 Climate Normals, 28°F — this town
- City area
- 7K 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 Clear Lake's average, not your lot's — a low corner or a tree line moves it. Against Clear Lake's 175-day season, see what your own ground reads.
Soil varies lot by lot — soil types explained.
What this means for growing in Clear Lake
Each reading below is measured for Clear Lake itself — here is what it means for a garden here, and the move an experienced grower makes about it.
Season length
MeasuredClear Lake 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
Winter hardiness
MeasuredClear Lake 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 Clear Lake is in
Clear Lake sits in the Western Corn Belt Plains — EPA Level III, inside the wider Great Plains. That is read at Clear Lake's own centroid rather than borrowed from Cerro Gordo County.
What Grows in Clear Lake
Every plant below cleared Clear Lake's own zone 5a and its 175-day season. Each card opens that plant's Iowa profile. How we score.
Is it too late to plant in Clear Lake?
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 22; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near Apr 19 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Oct 11 — 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 Clear Lake
Closest first, within ~10 miles of Clear Lake. Listing isn't leaking, and distance isn't exposure.
- PHOENIX OIL COUnderground Storage Tanks · 600 ft
- 106 HIGHWAY STANDARDUnderground Storage Tanks · 650 ft
- PUBLIC WORKS BUILDINGUnderground Storage Tanks · 850 ft
- CERRO GORDO COUNTY SEC ROAD DEPTUnderground Storage Tanks · 1200 ft
- Bayside Patrol Station/Clear Lake Dist OfficeUnderground Storage Tanks · 1400 ft
- TOM ASHLANDUnderground Storage Tanks · 1400 ft
- HARBOURAGE CONDOUnderground Storage Tanks · 1400 ft
- RUANUnderground Storage Tanks · 1400 ft
- UNISYS CORPORATIONToxics Release Inventory · 1500 ft
- CLASSIC INC DBA NEAL CLEANERSBrownfields · 1500 ft
- ZIEDLER CONCRETE PRODUCTSUnderground Storage Tanks · 1500 ft
- MIDLAND CONCRETE PRODUCTSToxics Release Inventory · 1500 ft
6 more sites are on the record inside the same radius. See them on the map
Measured from Clear Lake'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 Clear Lake.
Sources Checked
within ~10 miles of Clear Lake
Severity Distribution
within ~10 miles of Clear Lake
Highest-Severity Sites
Know Before You Grow
- •Underground tanks leak petroleum as they age — near a former filling station, test the soil.
- •Near a brownfield, raised beds of imported soil give your food clean ground.
- •On a private well, test for nitrates: above 10 mg/L the water needs treatment before irrigating.
Check your specific parcel in Clear Lake
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 Clear Lake average
Your land is one point inside Clear Lake
Everything above resolves to Clear Lake as a whole — one PHZM band and one 28°F frost record, read across 7K 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 Clear Lake Average
Clear Lake Average
- ●USDA Zones 5a, averaged across Clear Lake
- ●One soil character for all of Clear Lake
- ●Frost dates read at Clear Lake's scale: Apr 19 to Oct 11
YOUR Parcel
- ✓Your exact zone, not Clear Lake's 5a
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your specific parcel in Clear Lake
Pull a site-specific report for your exact address in Clear Lake, Iowa — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Clear Lake averages can't show:
We read public map data around Clear Lake — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Clear Lake average
How we know this about Clear Lake
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 Clear Lake’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 Clear Lake
When does frost risk typically end in Clear Lake?
The last hard freeze (28°F) in Clear Lake typically lands around Apr 19, 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 10.
When is the first frost in Clear Lake?
The first hard freeze (28°F) in Clear Lake typically arrives around Oct 11, per NOAA 1991–2020 climate normals — the point tender summer crops finish. Lighter frosts run ahead of it, near Sep 27, so the watching starts about Sep 11 — about 175 days after the spring freeze cleared.
How long is the growing season in Clear Lake?
Measured between 28°F hard freezes, Clear Lake sees about 175 frost-free days — roughly Apr 19 through Oct 11, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer May 10 to Sep 27, about 140 days.
Is the soil safe to grow vegetables in Clear Lake?
The federal record around Clear Lake is a meaningful one — 472 documented sites, mostly Underground Storage Tanks entries (252), the nearest Underground Storage Tanks record about 0.1 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.
How do I protect my plants from frost in Clear Lake?
From about Sep 11 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 11 (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 11. Hardy greens and roots shrug off light frost and sweeten after it — leave them in.
Everything above is measured at Clear Lake's scale — its 5a band and its 175-day season. Your yard writes its own version of Clear Lake'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 Clear Lake’s own scale
6 of the readings below were taken at Clear Lake's own scale — its own ~175-day season between 28°F freezes, the 6,899 acres it covers and 472 documented sites around it; 4 are borrowed from a wider read, named and linked below.
Measured here
- Clear Lake's own USDA hardiness band, zones 5aUSDA PHZM 2023
- Clear Lake's own 28°F hard-freeze dates, about Apr 19 and Oct 11 and the ~175-day span between themNOAA 1991–2020 Climate Normals
- 472 documented contamination sites on the federal record near Clear Lake, the closest Underground Storage Tanks record about 0.1 miles out from the town centreFederal environmental registers
- Clear Lake's boundary and the 6,899 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 5a and a ~175-day seasonGrowable Ground crop-matching engine
- The ecoregion at Clear Lake'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 Clear Lake's 6,899 acres read through its county's SSURGO summaryfrom Cerro Gordo County
- Growing-degree days and winter chill — measured county-wide only, so the county page carries themfrom Cerro Gordo 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 Cerro Gordo County
What this page can’t tell you
- The soil pH, drainage, sun hours, and frost pockets on any one lot among Clear Lake's 6,899 acreswhy one lot differs from the next →
- Which side of Clear Lake you're on — a low spot frosts first and a south wall warms early, and one normal is being asked to speak for all 6,899 acresreading your own microclimate →
- How close that record sits to YOUR lot — the closest Underground Storage Tanks record about 0.1 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 Clear Lake-wide figureread your own land →
More in Iowa
Wider growing context
What grows across IowaClear Lake sits outside our named growing regions, so Iowa as a whole is its closest context here.
Nearby growing guides