Hamilton City, California, sits in USDA hardiness zone 9b — a range where zone-matched perennials and frost-aware annual timing set what succeeds.
The conditions favor tomato, artichoke, fig, and california poppy, among others — though every individual site edits that list with its own soil, sun, and drainage.
Even in Hamilton City, 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 City 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 City — soil, climate, flood, and parcel records. How we handle your address.
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Hamilton City — the short answer
Hamilton City, California: USDA zone 9b, about 309 days between hard freezes, across 262 acres of town.
- USDA zone
- 9b
- USDA PHZM 2023
- Last hard freeze (28°F)
- Jan 30
- Glenn County normal — NOAA 1991–2020, nearest to this town
- First hard freeze (28°F)
- Dec 5
- Glenn County normal — NOAA 1991–2020, nearest to this town
- Days between freezes
- ~309
- Glenn County normal — NOAA 1991–2020, nearest to this town
- Town area
- 262 acres
- US Census TIGER/Line 2025
Every figure names the dataset it came from. No 30-year normal resolves at this town’s own centroid, so the hard-freeze dates are Glenn County’s — the closest measured record, labelled as such rather than passed off as local.
Hardiness Zone Range
Zone 9b is Hamilton City's average, not your lot's — a low corner or a tree line moves it. Against Hamilton City's 309-day season, see what your own ground reads.
Soil varies lot by lot — soil types explained.
What this means for growing in Hamilton City
Each reading below is measured for Hamilton City itself — here is what it means for a garden here, and the move an experienced grower makes about it.
Season length
From county recordsHamilton City runs about 309 days between hard freezes (read from Glenn County, the closest normal to Hamilton City) — close to year-round growing.
Frost is rarely the limit here; winter plantings are as real as summer ones, and the harder question is which crops shrug off the summer heat.
Grow cool-season crops through the mild winter, and choose heat-tolerant varieties for the summer beds.
NOAA 1991–2020 Climate Normals
Winter hardiness
MeasuredHamilton City sits in USDA hardiness zone 9b.
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 City is in
Hamilton City sits in the Central California Valley — EPA Level III, inside the wider Mediterranean California. That is read at Hamilton City's own centroid, and it is not what its county reads: Glenn County is mostly Central California Foothills and Coastal Mountains. The wider page above you is answering a different question about different ground.
What Grows in Hamilton City
Plants matched to Hamilton City's USDA zones 9b, ordered by how much hardiness margin each has here — the ones with room to spare at both ends of this town's band lead. Each links to its full growing profile.
Is it too late to plant in Hamilton City?
For most of the year, no — what changes is which crops still fit the days remaining. Cool-season crops can go in from around Jan 2; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near Jan 30 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Dec 5 — long-season crops need about 90 days of runway, quick greens only 30. And with a calendar this mild, the honest answer is that planting barely stops — winter opens seasons colder regions never see.
What's on the federal record near Hamilton City
Closest first, within ~10 miles of Hamilton City. Listing isn't leaking, and distance isn't exposure.
- LARKIN AUTO & ELECTRICBrownfields · 400 ft
- AMPLA HEALTH HAMILTON CITY MEDICALBrownfields · 550 ft
- Hamilton Gas and FoodUnderground Storage Tanks · 1400 ft
- HAMILTON GAS & FOODBrownfields · 1400 ft
- STONY CREEK ASPHALT PLANTBrownfields · 1400 ft
- SEVEN LUCKY FOOD MARTBrownfields · 1400 ft
- 7 Lucky Food MartUnderground Storage Tanks · 1400 ft
- SPRECKELS SUGAR COMPANYToxics Release Inventory · 1500 ft
- SPRECKELS SUGAR COMPANYBrownfields · 1500 ft
- Double EE MarketUnderground Storage Tanks · 1600 ft
- DOUBLE EE MARKETBrownfields · 1600 ft
- NUTRIEN AG SOLUTIONSBrownfields · 1600 ft
6 more sites are on the record inside the same radius. See them on the map
Measured from Hamilton City'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 City.
Total Sites
780
within ~10 miles of Hamilton City
Risk Level
Elevated
Highest-severity
8 Superfund sites (none NPL-listed)
Sources Checked
within ~10 miles of Hamilton City
Severity Distribution
within ~10 miles of Hamilton City
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around Hamilton City, two things run higher than the national average within ~10 miles of Hamilton City — Brownfields (474 sites) and Nitrate (250 sites). It's not cause for alarm — it's worth knowing, and there's a sensible way to grow around it.
Brownfields: Brownfield sites are former commercial or industrial properties where legacy soil contamination (heavy metals, PAHs, petroleum compounds) may persist.
Nitrate: Nitrate contamination primarily comes from agricultural fertilizer runoff and failing septic systems.
Check EPA brownfield remediation status — many sites have completed cleanup with institutional controls.
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 City
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 City average
Your land is one point inside Hamilton City
Everything above resolves to Hamilton City as a whole — one PHZM band, read across 262 acres, with hard-freeze dates borrowed from Glenn County’s record because no 30-year normal resolves at this town’s own centroid. 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 town 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 City Average
Hamilton City Average
- ●USDA Zones 9b, averaged across Hamilton City
- ●One soil character for all of Hamilton City
- ●Frost dates read at Hamilton City's scale: Jan 30 to Dec 5
YOUR Parcel
- ✓Your exact zone, not Hamilton City's 9b
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your specific parcel in Hamilton City
Pull a site-specific report for your exact address in Hamilton City, California — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Hamilton City averages can't show:
We read public map data around Hamilton City — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Hamilton City average
How we know this about Hamilton City
The datasets: hardiness from the USDA ARS Plant Hardiness Zone Map 2023, read at this town’s own centroid; hard-freeze dates from NOAA 1991–2020 28°F normals at Glenn County’s record, because none resolves here; 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 town grain anywhere on this page — there is no town-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 City
When does frost risk typically end in Hamilton City?
The last hard freeze (28°F) in Hamilton City typically lands around Jan 30, 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 Feb 20.
When is the first frost in Hamilton City?
The first hard freeze (28°F) in Hamilton City typically arrives around Dec 5, per NOAA 1991–2020 climate normals — the point tender summer crops finish. Lighter frosts run ahead of it, near Nov 21, so the watching starts about Nov 5 — about 309 days after the spring freeze cleared.
How long is the growing season in Hamilton City?
Measured between 28°F hard freezes, Hamilton City sees about 309 frost-free days — roughly Jan 30 through Dec 5, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer Feb 20 to Nov 21, about 274 days.
Is the soil safe to grow vegetables in Hamilton City?
The federal record around Hamilton City is a meaningful one — 780 documented sites, mostly Brownfields entries (474), the nearest Brownfields record under a tenth of a mile 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 City?
From about Nov 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 Dec 5 (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 Dec 5. Hardy greens and roots shrug off light frost and sweeten after it — leave them in.
Everything above is measured at Hamilton City's scale — its 9b band and its 309-day season. Your yard writes its own version of Hamilton City'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 City’s own scale
4 of the readings below were taken at Hamilton City's own scale — the 262 acres it covers and 780 documented sites around it; 6 are borrowed from a wider read, named and linked below.
Measured here
- Hamilton City's own USDA hardiness band, zones 9bUSDA PHZM 2023
- 780 documented contamination sites on the federal record near Hamilton City, the closest Brownfields record under a tenth of a mile out from the town centreFederal environmental registers
- Hamilton City's boundary and the 262 acres inside itUS Census TIGER/Line 2025
- Hamilton City sits in the Central California Valley — not the ecoregion its county mostly readsUS EPA Level III Ecoregions
Inherited from a wider read
- The 28°F hard-freeze dates — Hamilton City has no normal of its own, so its county's is the closest measured readfrom Glenn County
- Soil character — no town-scale survey exists, so Hamilton City's 262 acres read through its county's SSURGO summaryfrom Glenn County
- The candidate plant list — California's curated set, filtered to this zone band and re-ordered by how much margin each has herefrom California
- Growing-degree days and winter chill — measured county-wide only, so the county page carries themfrom Glenn County
- The growing challenges every California grower plans around — written at state scale, so they stay on the state guidefrom California
- Butterfly and beetle records, and the farmland pesticide estimate — all published county-widefrom Glenn County
What this page can’t tell you
- The soil pH, drainage, sun hours, and frost pockets on any one lot among Hamilton City's 262 acreswhy one lot differs from the next →
- Which side of Hamilton City you're on — a low spot frosts first and a south wall warms early, and one normal is being asked to speak for all 262 acresreading your own microclimate →
- How close that record sits to YOUR lot — the closest Brownfields 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 Hamilton City-wide figureread your own land →
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