Thayer, Iowa, sits in USDA hardiness zone 5b — a range where zone-matched perennials and frost-aware annual timing set what succeeds.
These conditions suit cabbage, cranberry, lavender, and collard greens — a starting list any specific site will trim or extend with its own soil, sun, and drainage.
Even in Thayer, 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 Thayer 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 Thayer — soil, climate, flood, and parcel records. How we handle your address.
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Thayer — the short answer
Thayer, Iowa: USDA zone 5b, about 192 days between hard freezes, across 92 acres of city.
- USDA zone
- 5b
- USDA PHZM 2023
- Last hard freeze (28°F)
- Apr 13
- NOAA 1991–2020 Climate Normals, 28°F — this town
- First hard freeze (28°F)
- Oct 22
- NOAA 1991–2020 Climate Normals, 28°F — this town
- Days between freezes
- ~192
- NOAA 1991–2020 Climate Normals, 28°F — this town
- City area
- 92 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 5b is Thayer's average, not your lot's — a low corner or a tree line moves it. Against Thayer's 192-day season, see what your own ground reads.
Soil varies lot by lot — soil types explained.
What this means for growing in Thayer
Each reading below is measured for Thayer itself — here is what it means for a garden here, and the move an experienced grower makes about it.
Season length
MeasuredThayer runs about 192 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
MeasuredThayer sits in USDA hardiness zone 5b.
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 Thayer is in
Thayer sits in the Western Corn Belt Plains — EPA Level III, inside the wider Great Plains. That is read at Thayer's own centroid rather than borrowed from Union County.
What Grows in Thayer
Every plant below cleared Thayer's own zone 5b and its 192-day season. Each card opens that plant's Iowa profile. How we score.
Is it too late to plant in Thayer?
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 16; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near Apr 13 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Oct 22 — 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 Thayer
Closest first, within ~10 miles of Thayer. Listing isn't leaking, and distance isn't exposure.
- 072N27W28CCC 1944Nitrate · 4.7 mi
- 072N27W32ADD 06859 1954Nitrate · 4.7 mi
- CASEYS GENERAL STORE 3332Underground Storage Tanks · 5.1 mi
- MURRAY COMMUNITY SCHOOLBrownfields · 5.1 mi
- 072N27W16AAANitrate · 5.1 mi
- 072N27W15BBC 01857 1944Murray Independent SchoolNitrate · 5.2 mi
- CLARKE COUNTY SECONDARY ROADSUnderground Storage Tanks · 5.2 mi
- BROWNS SERVICEUnderground Storage Tanks · 5.3 mi
- UNION LP GAS SYSTEMUnderground Storage Tanks · 5.3 mi
- 072N27W10CDCA 21135 1968Murray 1Nitrate · 5.4 mi
- DAVIDSON & SONSUnderground Storage Tanks · 5.4 mi
- 072N27W10AACC 11278 1959Murray 2Nitrate · 6.1 mi
6 more sites are on the record inside the same radius. See them on the map
Measured from Thayer'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 Thayer.
Total Sites
61
within ~10 miles of Thayer
Risk Level
Moderate
Highest-severity
1 Toxics Release Inventory facility
Sources Checked
within ~10 miles of Thayer
Severity Distribution
within ~10 miles of Thayer
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around Thayer, Nitrate runs higher than the national average — 40 sites within ~10 miles of Thayer. That's not a problem with your land — it's information about it.
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 Thayer
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 Thayer average
Your land is one point inside Thayer
Everything above resolves to Thayer as a whole — one PHZM band and one 28°F frost record, read across 92 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 Thayer Average
Thayer Average
- ●USDA Zones 5b, averaged across Thayer
- ●One soil character for all of Thayer
- ●Frost dates read at Thayer's scale: Apr 13 to Oct 22
YOUR Parcel
- ✓Your exact zone, not Thayer's 5b
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your specific parcel in Thayer
Pull a site-specific report for your exact address in Thayer, Iowa — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Thayer averages can't show:
We read public map data around Thayer — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Thayer average
How we know this about Thayer
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 Thayer’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 Thayer
When does frost risk typically end in Thayer?
The last hard freeze (28°F) in Thayer typically lands around Apr 13, 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 4.
When is the first frost in Thayer?
The first hard freeze (28°F) in Thayer typically arrives around Oct 22, per NOAA 1991–2020 climate normals — the point tender summer crops finish. Lighter frosts run ahead of it, near Oct 8, so the watching starts about Sep 22 — about 192 days after the spring freeze cleared.
How long is the growing season in Thayer?
Measured between 28°F hard freezes, Thayer sees about 192 frost-free days — roughly Apr 13 through Oct 22, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer May 4 to Oct 8, about 157 days.
Is the soil safe to grow vegetables in Thayer?
The federal record around Thayer shows 61 documented sites, mostly Nitrate entries (40), the nearest Nitrate record about 4.7 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 Thayer?
From about Sep 22 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 22 (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 22. Hardy greens and roots shrug off light frost and sweeten after it — leave them in.
Everything above is measured at Thayer's scale — its 5b band and its 192-day season. Your yard writes its own version of Thayer'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 Thayer’s own scale
6 of the readings below were taken at Thayer's own scale — its own ~192-day season between 28°F freezes, the 92 acres it covers and 61 documented sites around it; 4 are borrowed from a wider read, named and linked below.
Measured here
- Thayer's own USDA hardiness band, zones 5bUSDA PHZM 2023
- Thayer's own 28°F hard-freeze dates, about Apr 13 and Oct 22 and the ~192-day span between themNOAA 1991–2020 Climate Normals
- 61 documented contamination sites on the federal record near Thayer, the closest Nitrate record about 4.7 miles out from the town centreFederal environmental registers
- Thayer's boundary and the 92 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 5b and a ~192-day seasonGrowable Ground crop-matching engine
- The ecoregion at Thayer'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 Thayer's 92 acres read through its county's SSURGO summaryfrom Union County
- Growing-degree days and winter chill — measured county-wide only, so the county page carries themfrom Union 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 Union County
What this page can’t tell you
- The soil pH, drainage, sun hours, and frost pockets on any one lot among Thayer's 92 acreswhy one lot differs from the next →
- Which side of Thayer you're on — a low spot frosts first and a south wall warms early, and one normal is being asked to speak for all 92 acresreading your own microclimate →
- How close that record sits to YOUR lot — the closest Nitrate record about 4.7 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 Thayer-wide figureread your own land →
More in Iowa
Wider growing context
What grows across IowaThayer sits outside our named growing regions, so Iowa as a whole is its closest context here.
Nearby growing guides