Hamilton, Illinois, sits in USDA hardiness zone 6a — a band that supports both cool-season staples and warm-season crops chosen to fit the local frost window.
Well-matched crops include cabbage, blueberry, lavender, and collard greens, and the gap between "grows in the area" and "grows in your yard" is closed by soil, sun, and drainage.
Even in Hamilton, 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 Hamilton 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 Hamilton — soil, climate, flood, and parcel records. How we handle your address.
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Hamilton — the short answer
Hamilton, Illinois: USDA zone 6a, about 221 days between hard freezes, across 2K acres of city.
- USDA zone
- 6a
- USDA PHZM 2023
- Last hard freeze (28°F)
- Mar 28
- NOAA 1991–2020 Climate Normals, 28°F — this town
- First hard freeze (28°F)
- Nov 4
- NOAA 1991–2020 Climate Normals, 28°F — this town
- Days between freezes
- ~221
- NOAA 1991–2020 Climate Normals, 28°F — this town
- City area
- 2K 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 6a is Hamilton's average, not your lot's — a low corner or a tree line moves it. Against Hamilton's 221-day season, see what your own ground reads.
Soil varies lot by lot — soil types explained.
What this means for growing in Hamilton
Each reading below is measured for Hamilton itself — here is what it means for a garden here, and the move an experienced grower makes about it.
Season length
MeasuredHamilton runs about 221 days between hard freezes — a long growing season.
There is slack for succession plantings and slow-finishing crops: many vegetables can be sown twice, and the heat-lovers have time to ripen fully.
Plan a second sowing of quick crops after the first comes out, and use the fall window most gardeners let sit idle.
NOAA 1991–2020 Climate Normals
Winter hardiness
MeasuredHamilton sits in USDA hardiness zone 6a.
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 Hamilton is in
Hamilton sits in the Interior River Valleys and Hills — EPA Level III, inside the wider Eastern Temperate Forests. That is read at Hamilton's own centroid rather than borrowed from Hancock County.
What Grows in Hamilton
Every plant below cleared Hamilton's own zone 6a and its 221-day season. Each card opens that plant's Illinois profile. How we score.
Is it too late to plant in Hamilton?
Usually not — gardeners here simply switch what goes in the ground as the season moves. Cool-season crops can go in from around Feb 28; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near Mar 28 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Nov 4 — long-season crops need about 90 days of runway, quick greens only 30. With a season this long, “too late” mostly means “switch crops” — second sowings and a full fall garden are the norm, with garlic closing the year.
What's on the federal record near Hamilton
Closest first, within ~10 miles of Hamilton. Listing isn't leaking, and distance isn't exposure.
- DADANT & SONS INCBrownfields · 1700 ft
- W L MILLER COBrownfields · 2200 ft
- AMEREN UE - KEOKUK PLANTBrownfields · 0.7 mi
- US ARMY CORPS OF ENGINEERS LOCK & DAM 19Brownfields · 0.8 mi
- Muegge Auto SalvageUnderground Storage Tanks · 0.8 mi
- Hamilton City OfUnderground Storage Tanks · 0.9 mi
- Casey's General StoreUnderground Storage Tanks · 0.9 mi
- Kavanagh GarageUnderground Storage Tanks · 1.0 mi
- Hamilton Comm Cons Sch #328Underground Storage Tanks · 1.0 mi
- CASEY''S GENERAL STORE 2595Underground Storage Tanks · 1.1 mi
- ARTISTIC CLEANERS - KEOKUKBrownfields · 1.1 mi
- AyercoUnderground Storage Tanks · 1.2 mi
6 more sites are on the record inside the same radius. See them on the map
Measured from Hamilton'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 Hamilton.
Sources Checked
within ~10 miles of Hamilton
Severity Distribution
within ~10 miles of Hamilton
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around Hamilton, Toxics Release Inventory runs higher than the national average — 17 sites within ~10 miles of Hamilton. It's not cause for alarm — it's worth knowing, and there's a sensible way to grow around it.
Toxics Release Inventory: TRI facilities report annual chemical releases to air, water, and land.
Check prevailing wind direction — downwind parcels face higher exposure than upwind or crosswind locations.
Check your specific parcel in Hamilton
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 Hamilton average
Your land is one point inside Hamilton
Everything above resolves to Hamilton as a whole — one PHZM band and one 28°F frost record, read across 2K 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 Hamilton Average
Hamilton Average
- ●USDA Zones 6a, averaged across Hamilton
- ●One soil character for all of Hamilton
- ●Frost dates read at Hamilton's scale: Mar 28 to Nov 4
YOUR Parcel
- ✓Your exact zone, not Hamilton's 6a
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your specific parcel in Hamilton
Pull a site-specific report for your exact address in Hamilton, Illinois — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Hamilton averages can't show:
We read public map data around Hamilton — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Hamilton average
How we know this about Hamilton
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 Hamilton’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 Hamilton
When does frost risk typically end in Hamilton?
The last hard freeze (28°F) in Hamilton typically lands around Mar 28, 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 Apr 18.
When is the first frost in Hamilton?
The first hard freeze (28°F) in Hamilton typically arrives around Nov 4, per NOAA 1991–2020 climate normals — the point tender summer crops finish. Lighter frosts run ahead of it, near Oct 21, so the watching starts about Oct 5 — about 221 days after the spring freeze cleared.
How long is the growing season in Hamilton?
Measured between 28°F hard freezes, Hamilton sees about 221 frost-free days — roughly Mar 28 through Nov 4, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer Apr 18 to Oct 21, about 186 days.
Is the soil safe to grow vegetables in Hamilton?
The federal record around Hamilton is a meaningful one — 178 documented sites, mostly Underground Storage Tanks entries (85), the nearest Brownfields record about 0.3 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 Hamilton?
From about Oct 5 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 Nov 4 (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 Nov 4. Hardy greens and roots shrug off light frost and sweeten after it — leave them in.
Everything above is measured at Hamilton's scale — its 6a band and its 221-day season. Your yard writes its own version of Hamilton'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 Hamilton’s own scale
6 of the readings below were taken at Hamilton's own scale — its own ~221-day season between 28°F freezes, the 2,279 acres it covers and 178 documented sites around it; 4 are borrowed from a wider read, named and linked below.
Measured here
- Hamilton's own USDA hardiness band, zones 6aUSDA PHZM 2023
- Hamilton's own 28°F hard-freeze dates, about Mar 28 and Nov 4 and the ~221-day span between themNOAA 1991–2020 Climate Normals
- 178 documented contamination sites on the federal record near Hamilton, the closest Brownfields record about 0.3 miles out from the town centreFederal environmental registers
- Hamilton's boundary and the 2,279 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 6a and a ~221-day seasonGrowable Ground crop-matching engine
- The ecoregion at Hamilton's own centroid, the Interior River Valleys and HillsUS EPA Level III Ecoregions
Inherited from a wider read
- Soil character — no town-scale survey exists, so Hamilton's 2,279 acres read through its county's SSURGO summaryfrom Hancock County
- Growing-degree days and winter chill — measured county-wide only, so the county page carries themfrom Hancock County
- The growing challenges every Illinois grower plans around — written at state scale, so they stay on the state guidefrom Illinois
- Butterfly and beetle records, and the farmland pesticide estimate — all published county-widefrom Hancock County
What this page can’t tell you
- The soil pH, drainage, sun hours, and frost pockets on any one lot among Hamilton's 2,279 acreswhy one lot differs from the next →
- Which side of Hamilton you're on — a low spot frosts first and a south wall warms early, and one normal is being asked to speak for all 2,279 acresreading your own microclimate →
- How close that record sits to YOUR lot — the closest Brownfields record about 0.3 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 Hamilton-wide figureread your own land →
More in Illinois
Wider growing context
What grows across IllinoisHamilton sits outside our named growing regions, so Illinois as a whole is its closest context here.