Hamilton, Montana, sits in USDA hardiness zone 5b — a band that supports both cool-season staples and warm-season crops chosen to fit the local frost window.
Well-matched crops include cabbage, cranberry, 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, Montana: USDA zone 5b, about 152 days between hard freezes, across 2K acres of city.
- USDA zone
- 5b
- USDA PHZM 2023
- Last hard freeze (28°F)
- May 4
- NOAA 1991–2020 Climate Normals, 28°F — this town
- First hard freeze (28°F)
- Oct 3
- NOAA 1991–2020 Climate Normals, 28°F — this town
- Days between freezes
- ~152
- 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 5b is Hamilton's average, not your lot's — a low corner or a tree line moves it. Against Hamilton's 152-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 152 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
MeasuredHamilton 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 Hamilton is in
Hamilton sits in the Middle Rockies — EPA Level III, inside the wider Northwestern Forested Mountains. That is read at Hamilton's own centroid, and it is not what its county reads: Ravalli County is mostly Idaho Batholith. The wider page above you is answering a different question about different ground.
What Grows in Hamilton
Every plant below cleared Hamilton's own zone 5b and its 152-day season. Each card opens that plant's Montana 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 Apr 6; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near May 4 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Oct 3 — 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 Hamilton
Closest first, within ~10 miles of Hamilton. Listing isn't leaking, and distance isn't exposure.
- 06N21W25AA 01Nitrate · 700 ft
- HAZELTINE PROPERTYUnderground Storage Tanks · 950 ft
- GAS N GRUBUnderground Storage Tanks · 1000 ft
- COLUMBIA PAINT & COATINGS CO HAMILTONBrownfields · 1100 ft
- QUALITY USED CARSUnderground Storage Tanks · 1100 ft
- 06N21W25AD 01Nitrate · 1200 ft
- HAMILTON SCHOOL DISTRICT #3 WASHINGTON ELEMENTARY SCHOOLBrownfields · 1200 ft
- CITY OF HAMILTON USTUnderground Storage Tanks · 1300 ft
- RIBI IMMUNOCHEM RESEARCH INCUnderground Storage Tanks · 1300 ft
- ERNIE BUCHHOLZUnderground Storage Tanks · 1400 ft
- S & S AUTO BODYBrownfields · 1400 ft
- BITTERROOT PLUMBING HEATING AND ELECTRIC INCUnderground Storage Tanks · 1500 ft
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.
Total Sites
408
within ~10 miles of Hamilton
Risk Level
Elevated
Highest-severity
2 Toxics Release Inventory facilities
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, Nitrate runs higher than the national average — 330 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.
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 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 5b, averaged across Hamilton
- ●One soil character for all of Hamilton
- ●Frost dates read at Hamilton's scale: May 4 to Oct 3
YOUR Parcel
- ✓Your exact zone, not Hamilton's 5b
- ✓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, Montana — 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 May 4, 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 25.
When is the first frost in Hamilton?
The first hard freeze (28°F) in Hamilton typically arrives around Oct 3, per NOAA 1991–2020 climate normals — the point tender summer crops finish. Lighter frosts run ahead of it, near Sep 19, so the watching starts about Sep 3 — about 152 days after the spring freeze cleared.
How long is the growing season in Hamilton?
Measured between 28°F hard freezes, Hamilton sees about 152 frost-free days — roughly May 4 through Oct 3, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer May 25 to Sep 19, about 117 days.
Is the soil safe to grow vegetables in Hamilton?
The federal record around Hamilton is a meaningful one — 408 documented sites, mostly Nitrate entries (330), the nearest Nitrate 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 Hamilton?
From about Sep 3 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 3 (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 3. Hardy greens and roots shrug off light frost and sweeten after it — leave them in.
Everything above is measured at Hamilton's scale — its 5b band and its 152-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 ~152-day season between 28°F freezes, the 1,628 acres it covers and 408 documented sites around it; 4 are borrowed from a wider read, named and linked below.
Measured here
- Hamilton's own USDA hardiness band, zones 5bUSDA PHZM 2023
- Hamilton's own 28°F hard-freeze dates, about May 4 and Oct 3 and the ~152-day span between themNOAA 1991–2020 Climate Normals
- 408 documented contamination sites on the federal record near Hamilton, the closest Nitrate record about 0.1 miles out from the town centreFederal environmental registers
- Hamilton's boundary and the 1,628 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 5b and a ~152-day seasonGrowable Ground crop-matching engine
- Hamilton sits in the Middle Rockies — not the ecoregion its county mostly readsUS EPA Level III Ecoregions
Inherited from a wider read
- Soil character — no town-scale survey exists, so Hamilton's 1,628 acres read through its county's SSURGO summaryfrom Ravalli County
- Growing-degree days and winter chill — measured county-wide only, so the county page carries themfrom Ravalli County
- The growing challenges every Montana grower plans around — written at state scale, so they stay on the state guidefrom Montana
- Butterfly and beetle records, and the farmland pesticide estimate — all published county-widefrom Ravalli County
What this page can’t tell you
- The soil pH, drainage, sun hours, and frost pockets on any one lot among Hamilton's 1,628 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 1,628 acresreading your own microclimate →
- How close that record sits to YOUR lot — the closest Nitrate 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 Hamilton-wide figureread your own land →
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