Humboldt Hill, California, sits in USDA hardiness zone 9b — a band that supports both cool-season staples and warm-season crops chosen to fit the local frost window.
Expect okra, meyer lemon, california poppy, and artichoke to be strong candidates here; the deciding factors on any one parcel stay local — soil, sun, and drainage.
Even in Humboldt Hill, 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 Humboldt Hill 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 Humboldt Hill — soil, climate, flood, and parcel records. How we handle your address.
No card required · your full report in seconds
Humboldt Hill — the short answer
Humboldt Hill, California: USDA zone 9b, about 278 days between hard freezes, across 3K acres of town.
- USDA zone
- 9b
- USDA PHZM 2023
- Last hard freeze (28°F)
- Mar 1
- Humboldt County normal — NOAA 1991–2020, nearest to this town
- First hard freeze (28°F)
- Dec 4
- Humboldt County normal — NOAA 1991–2020, nearest to this town
- Days between freezes
- ~278
- Humboldt County normal — NOAA 1991–2020, nearest to this town
- Town area
- 3K 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 Humboldt County’s — the closest measured record, labelled as such rather than passed off as local.
Hardiness Zone Range
Zone 9b is Humboldt Hill's average, not your lot's — a low corner or a tree line moves it. Against Humboldt Hill's 278-day season, see what your own ground reads.
Soil varies lot by lot — soil types explained.
What this means for growing in Humboldt Hill
Each reading below is measured for Humboldt Hill itself — here is what it means for a garden here, and the move an experienced grower makes about it.
Season length
From county recordsHumboldt Hill runs about 278 days between hard freezes (read from Humboldt County, the closest normal to Humboldt Hill) — 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
MeasuredHumboldt Hill 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 Humboldt Hill is in
Humboldt Hill sits in the Coast Range — EPA Level III, inside the wider Marine West Coast Forest. That is read at Humboldt Hill's own centroid rather than borrowed from Humboldt County.
What Grows in Humboldt Hill
Every plant below cleared Humboldt Hill's own zone 9b and its 278-day season. Each card opens that plant's California profile. How we score.
Is it too late to plant in Humboldt Hill?
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 Feb 1; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near Mar 1 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Dec 4 — long-season crops need about 90 days of runway, quick greens only 30. In a climate this gentle, “too late” hardly applies — the question becomes which crops prefer the cooler months ahead.
What's on the federal record near Humboldt Hill
Closest first, within ~10 miles of Humboldt Hill. Listing isn't leaking, and distance isn't exposure.
- PARKER & SON INCBrownfields · 1000 ft
- COUNTY OF HUMBOLDTBrownfields · 1.0 mi
- 004N001W16H001HNitrate · 1.0 mi
- SOUTH BAY UNION SCHOOL DISTRICTBrownfields · 1.0 mi
- ENVIRONMENTAL TECHNOLOGY INCBrownfields · 1.1 mi
- ENVIRONMENTAL TECHNOLOGY INCToxics Release Inventory · 1.1 mi
- RAO CONSTRUCTION CO INCBrownfields · 1.1 mi
- PATRICK MURPHY LOGGINGBrownfields · 1.1 mi
- HUMBOLDT BAY HARBOR RECREATION & CONSERVBrownfields · 1.2 mi
- HUMBOLDT C.S.D.PFAS · 1.2 mi
- PGE HUMBOLDT BAY GENERATING STATIONToxics Release Inventory · 1.2 mi
- E.G. AYERS DISTRIBUTING INCBrownfields · 1.2 mi
6 more sites are on the record inside the same radius. See them on the map
Measured from Humboldt Hill'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 Humboldt Hill.
Total Sites
469
within ~10 miles of Humboldt Hill
Risk Level
Elevated
Highest-severity
6 Superfund sites (none NPL-listed)
Sources Checked
within ~10 miles of Humboldt Hill
Severity Distribution
within ~10 miles of Humboldt Hill
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around Humboldt Hill, two things run higher than the national average within ~10 miles of Humboldt Hill — CAFO (8 sites) and Brownfields (381 sites). That's not a problem with your land — it's information about it.
CAFO: CAFOs pose a different contamination profile than chemical sources.
Brownfields: Brownfield sites are former commercial or industrial properties where legacy soil contamination (heavy metals, PAHs, petroleum compounds) may persist.
Wash all produce consumed raw thoroughly, especially leafy greens grown near CAFOs.
Check EPA brownfield remediation status — many sites have completed cleanup with institutional controls.
Check your specific parcel in Humboldt Hill
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 Humboldt Hill average
Your land is one point inside Humboldt Hill
Everything above resolves to Humboldt Hill as a whole — one PHZM band, read across 3K acres, with hard-freeze dates borrowed from Humboldt 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 Humboldt Hill Average
Humboldt Hill Average
- ●USDA Zones 9b, averaged across Humboldt Hill
- ●One soil character for all of Humboldt Hill
- ●Frost dates read at Humboldt Hill's scale: Mar 1 to Dec 4
YOUR Parcel
- ✓Your exact zone, not Humboldt Hill's 9b
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your specific parcel in Humboldt Hill
Pull a site-specific report for your exact address in Humboldt Hill, California — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Humboldt Hill averages can't show:
We read public map data around Humboldt Hill — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Humboldt Hill average
How we know this about Humboldt Hill
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 Humboldt 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 Humboldt Hill
When does frost risk typically end in Humboldt Hill?
The last hard freeze (28°F) in Humboldt Hill typically lands around Mar 1, 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 Mar 22.
When is the first frost in Humboldt Hill?
The first hard freeze (28°F) in Humboldt Hill typically arrives around Dec 4, per NOAA 1991–2020 climate normals — the point tender summer crops finish. Lighter frosts run ahead of it, near Nov 20, so the watching starts about Nov 4 — about 278 days after the spring freeze cleared.
How long is the growing season in Humboldt Hill?
Measured between 28°F hard freezes, Humboldt Hill sees about 278 frost-free days — roughly Mar 1 through Dec 4, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer Mar 22 to Nov 20, about 243 days.
Is the soil safe to grow vegetables in Humboldt Hill?
The federal record around Humboldt Hill is a meaningful one — 469 documented sites, mostly Brownfields entries (381), the nearest Brownfields record about 0.2 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 Humboldt Hill?
From about Nov 4 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 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 Dec 4. Hardy greens and roots shrug off light frost and sweeten after it — leave them in.
Everything above is measured at Humboldt Hill's scale — its 9b band and its 278-day season. Your yard writes its own version of Humboldt Hill'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 Humboldt Hill’s own scale
5 of the readings below were taken at Humboldt Hill's own scale — the 2,659 acres it covers and 469 documented sites around it; 5 are borrowed from a wider read, named and linked below.
Measured here
- Humboldt Hill's own USDA hardiness band, zones 9bUSDA PHZM 2023
- 469 documented contamination sites on the federal record near Humboldt Hill, the closest Brownfields record about 0.2 miles out from the town centreFederal environmental registers
- Humboldt Hill's boundary and the 2,659 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 9b and a ~278-day seasonGrowable Ground crop-matching engine
- The ecoregion at Humboldt Hill's own centroid, the Coast RangeUS EPA Level III Ecoregions
Inherited from a wider read
- The 28°F hard-freeze dates — Humboldt Hill has no normal of its own, so its county's is the closest measured readfrom Humboldt County
- Soil character — no town-scale survey exists, so Humboldt Hill's 2,659 acres read through its county's SSURGO summaryfrom Humboldt County
- Growing-degree days and winter chill — measured county-wide only, so the county page carries themfrom Humboldt 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 Humboldt County
What this page can’t tell you
- The soil pH, drainage, sun hours, and frost pockets on any one lot among Humboldt Hill's 2,659 acreswhy one lot differs from the next →
- Which side of Humboldt Hill you're on — a low spot frosts first and a south wall warms early, and one normal is being asked to speak for all 2,659 acresreading your own microclimate →
- How close that record sits to YOUR lot — the closest Brownfields record about 0.2 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 Humboldt Hill-wide figureread your own land →
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