Post Mountain, California, sits in USDA hardiness zone 8b — a band that supports both cool-season staples and warm-season crops chosen to fit the local frost window.
The conditions favor cabbage, fig, california poppy, and collard greens, among others — though every individual site edits that list with its own soil, sun, and drainage.
Even in Post Mountain, 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 Post Mountain 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 Post Mountain — soil, climate, flood, and parcel records. How we handle your address.
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Post Mountain — the short answer
Post Mountain, California: USDA zone 8b, about 203 days between hard freezes, across 8K acres of town.
- USDA zone
- 8b
- USDA PHZM 2023
- Last hard freeze (28°F)
- Apr 20
- NOAA 1991–2020 Climate Normals, 28°F — this town
- First hard freeze (28°F)
- Nov 9
- NOAA 1991–2020 Climate Normals, 28°F — this town
- Days between freezes
- ~203
- NOAA 1991–2020 Climate Normals, 28°F — this town
- Town area
- 8K 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 8b is Post Mountain's average, not your lot's — a low corner or a tree line moves it. Against Post Mountain's 203-day season, see what your own ground reads.
Soil varies lot by lot — soil types explained.
What this means for growing in Post Mountain
Each reading below is measured for Post Mountain itself — here is what it means for a garden here, and the move an experienced grower makes about it.
Season length
MeasuredPost Mountain runs about 203 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
MeasuredPost Mountain sits in USDA hardiness zone 8b.
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 Post Mountain is in
Post Mountain sits in the Klamath Mountains/California High North Coast Range — EPA Level III, inside the wider Northwestern Forested Mountains. That is read at Post Mountain's own centroid rather than borrowed from Trinity County.
What Grows in Post Mountain
Every plant below cleared Post Mountain's own zone 8b and its 203-day season. Each card opens that plant's California profile. How we score.
Is it too late to plant in Post Mountain?
Almost never — the real question is what to plant next. Cool-season crops can go in from around Mar 23; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near Apr 20 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Nov 9 — long-season crops need about 90 days of runway, quick greens only 30. A long window like this one runs successions deep into fall — and even its last weeks take quick greens and garlic.
What's on the federal record near Post Mountain
Closest first, within ~10 miles of Post Mountain. Listing isn't leaking, and distance isn't exposure.
- Black Jack OccurrenceMining · 1800 ft
- Black JackMining · 0.6 mi
- Twin CedarsMining · 0.9 mi
- Federal ClaimMining · 1.1 mi
- FederalMining · 1.1 mi
- Compass OccurrenceMining · 1.4 mi
- Pewee ClaimMining · 1.4 mi
- CompassMining · 1.4 mi
- Peewee ProspectMining · 1.4 mi
- Empire ClaimMining · 1.9 mi
- Western Chrome 3 and 4Mining · 2.1 mi
- UnnamedMining · 2.1 mi
6 more sites are on the record inside the same radius. See them on the map
Measured from Post Mountain'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 Post Mountain.
Severity Distribution
within ~10 miles of Post Mountain
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around Post Mountain, Mining runs higher than the national average — 72 sites within ~10 miles of Post Mountain. Knowing it is half the work — and it's nothing a thoughtful grower can't plan for.
Mining: Mining sites — both historic and active — can leach heavy metals (arsenic, lead, cadmium, mercury) into soil and water for centuries after operations cease.
Test soil for heavy metals (lead, arsenic, cadmium, mercury) — this is essential near any mining site.
Check your specific parcel in Post Mountain
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 Post Mountain average
Your land is one point inside Post Mountain
Everything above resolves to Post Mountain as a whole — one PHZM band and one 28°F frost record, read across 8K 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 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 Post Mountain Average
Post Mountain Average
- ●USDA Zones 8b, averaged across Post Mountain
- ●One soil character for all of Post Mountain
- ●Frost dates read at Post Mountain's scale: Apr 20 to Nov 9
YOUR Parcel
- ✓Your exact zone, not Post Mountain's 8b
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your specific parcel in Post Mountain
Pull a site-specific report for your exact address in Post Mountain, California — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Post Mountain averages can't show:
We read public map data around Post Mountain — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Post Mountain average
How we know this about Post Mountain
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 Post Mountain’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 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 Post Mountain
When does frost risk typically end in Post Mountain?
The last hard freeze (28°F) in Post Mountain typically lands around Apr 20, 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 11.
When is the first frost in Post Mountain?
The first hard freeze (28°F) in Post Mountain typically arrives around Nov 9, per NOAA 1991–2020 climate normals — the point tender summer crops finish. Lighter frosts run ahead of it, near Oct 26, so the watching starts about Oct 10 — about 203 days after the spring freeze cleared.
How long is the growing season in Post Mountain?
Measured between 28°F hard freezes, Post Mountain sees about 203 frost-free days — roughly Apr 20 through Nov 9, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer May 11 to Oct 26, about 168 days.
Is the soil safe to grow vegetables in Post Mountain?
The federal record around Post Mountain shows 85 documented sites, mostly Mining entries (72), the nearest Mining record about 0.3 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 Post Mountain?
From about Oct 10 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 9 (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 9. Hardy greens and roots shrug off light frost and sweeten after it — leave them in.
Everything above is measured at Post Mountain's scale — its 8b band and its 203-day season. Your yard writes its own version of Post Mountain'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 Post Mountain’s own scale
6 of the readings below were taken at Post Mountain's own scale — its own ~203-day season between 28°F freezes, the 7,944 acres it covers and 85 documented sites around it; 4 are borrowed from a wider read, named and linked below.
Measured here
- Post Mountain's own USDA hardiness band, zones 8bUSDA PHZM 2023
- Post Mountain's own 28°F hard-freeze dates, about Apr 20 and Nov 9 and the ~203-day span between themNOAA 1991–2020 Climate Normals
- 85 documented contamination sites on the federal record near Post Mountain, the closest Mining record about 0.3 miles out from the town centreFederal environmental registers
- Post Mountain's boundary and the 7,944 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 8b and a ~203-day seasonGrowable Ground crop-matching engine
- The ecoregion at Post Mountain's own centroid, the Klamath Mountains/California High North Coast RangeUS EPA Level III Ecoregions
Inherited from a wider read
- Soil character — no town-scale survey exists, so Post Mountain's 7,944 acres read through its county's SSURGO summaryfrom Trinity County
- Growing-degree days and winter chill — measured county-wide only, so the county page carries themfrom Trinity 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 Trinity County
What this page can’t tell you
- The soil pH, drainage, sun hours, and frost pockets on any one lot among Post Mountain's 7,944 acreswhy one lot differs from the next →
- Which side of Post Mountain you're on — a low spot frosts first and a south wall warms early, and one normal is being asked to speak for all 7,944 acresreading your own microclimate →
- How close that record sits to YOUR lot — the closest Mining 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 Post Mountain-wide figureread your own land →
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