Diablo Grande, California, sits in USDA hardiness zone 9b — enough range to grow cool-season vegetables, hardy fruit, and warm-season crops that mature before the first hard frost.
Crops well matched to these conditions include okra, meyer lemon, california poppy, and artichoke — though what thrives on any one site still turns on its specific soil, sun, and drainage.
Even in Diablo Grande, 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 Diablo Grande 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 Diablo Grande — soil, climate, flood, and parcel records. How we handle your address.
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Diablo Grande — the short answer
Diablo Grande, California: USDA zone 9b, about 322 days between hard freezes, across 3K acres of town.
- USDA zone
- 9b
- USDA PHZM 2023
- Last hard freeze (28°F)
- Jan 22
- Stanislaus County normal — NOAA 1991–2020, nearest to this town
- First hard freeze (28°F)
- Dec 10
- Stanislaus County normal — NOAA 1991–2020, nearest to this town
- Days between freezes
- ~322
- Stanislaus 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 Stanislaus County’s — the closest measured record, labelled as such rather than passed off as local.
Hardiness Zone Range
Zone 9b is Diablo Grande's average, not your lot's — a low corner or a tree line moves it. Against Diablo Grande's 322-day season, see what your own ground reads.
Soil varies lot by lot — soil types explained.
What this means for growing in Diablo Grande
Each reading below is measured for Diablo Grande itself — here is what it means for a garden here, and the move an experienced grower makes about it.
Season length
From county recordsDiablo Grande runs about 322 days between hard freezes (read from Stanislaus County, the closest normal to Diablo Grande) — 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
MeasuredDiablo Grande 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 Diablo Grande is in
Diablo Grande sits in the Central California Foothills and Coastal Mountains — EPA Level III, inside the wider Mediterranean California. That is read at Diablo Grande's own centroid, and it is not what its county reads: Stanislaus County is mostly Central California Valley. The wider page above you is answering a different question about different ground.
What Grows in Diablo Grande
Every plant below cleared Diablo Grande's own zone 9b and its 322-day season. Each card opens that plant's California profile. How we score.
Is it too late to plant in Diablo Grande?
Almost never — the real question is what to plant next. Cool-season crops can go in from around Jan 1; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near Jan 22 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Dec 10 — 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 Diablo Grande
Closest first, within ~10 miles of Diablo Grande. Listing isn't leaking, and distance isn't exposure.
- CENTRAL VALLEY AG GRINDINGBrownfields · 0.7 mi
- PATTERSON, CITY OFPFAS · 1.8 mi
- Copper Mtn and Wild WestMining · 3.1 mi
- PHILLIPS 66 PATTERSON PUMP STATIONBrownfields · 6.3 mi
- Winegar ProspectMining · 6.4 mi
- Chevron PattersonUnderground Storage Tanks · 6.6 mi
- TEG INVESTMENTS CHEVRON GAS STATIONBrownfields · 6.6 mi
- Rania Oil Company (singh Unocal)Underground Storage Tanks · 6.6 mi
- RANIA OIL COBrownfields · 6.6 mi
- Patterson ValeroUnderground Storage Tanks · 6.7 mi
- Patterson MobilUnderground Storage Tanks · 6.7 mi
- UPS FREIGHTBrownfields · 6.7 mi
6 more sites are on the record inside the same radius. See them on the map
Measured from Diablo Grande'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 Diablo Grande.
Total Sites
221
within ~10 miles of Diablo Grande
Risk Level
Elevated
Highest-severity
1 Superfund site (none NPL-listed)
Sources Checked
within ~10 miles of Diablo Grande
Severity Distribution
within ~10 miles of Diablo Grande
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around Diablo Grande, two things run higher than the national average within ~10 miles of Diablo Grande — Mining (30 sites) and Brownfields (121 sites). It's not cause for alarm — it's worth knowing, and there's a sensible way to grow around it.
Mining: Mining sites — both historic and active — can leach heavy metals (arsenic, lead, cadmium, mercury) into soil and water for centuries after operations cease.
Brownfields: Brownfield sites are former commercial or industrial properties where legacy soil contamination (heavy metals, PAHs, petroleum compounds) may persist.
Test soil for heavy metals (lead, arsenic, cadmium, mercury) — this is essential near any mining site.
Check EPA brownfield remediation status — many sites have completed cleanup with institutional controls.
Check your specific parcel in Diablo Grande
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 Diablo Grande average
Your land is one point inside Diablo Grande
Everything above resolves to Diablo Grande as a whole — one PHZM band, read across 3K acres, with hard-freeze dates borrowed from Stanislaus 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 Diablo Grande Average
Diablo Grande Average
- ●USDA Zones 9b, averaged across Diablo Grande
- ●One soil character for all of Diablo Grande
- ●Frost dates read at Diablo Grande's scale: Jan 22 to Dec 10
YOUR Parcel
- ✓Your exact zone, not Diablo Grande's 9b
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your specific parcel in Diablo Grande
Pull a site-specific report for your exact address in Diablo Grande, California — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Diablo Grande averages can't show:
We read public map data around Diablo Grande — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Diablo Grande average
How we know this about Diablo Grande
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 Stanislaus 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 Diablo Grande
When does frost risk typically end in Diablo Grande?
The last hard freeze (28°F) in Diablo Grande typically lands around Jan 22, 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 12.
When is the first frost in Diablo Grande?
The first hard freeze (28°F) in Diablo Grande typically arrives around Dec 10, per NOAA 1991–2020 climate normals — the point tender summer crops finish. Lighter frosts run ahead of it, near Nov 26, so the watching starts about Nov 10 — about 322 days after the spring freeze cleared.
How long is the growing season in Diablo Grande?
Measured between 28°F hard freezes, Diablo Grande sees about 322 frost-free days — roughly Jan 22 through Dec 10, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer Feb 12 to Nov 26, about 287 days.
Is the soil safe to grow vegetables in Diablo Grande?
The federal record around Diablo Grande is a meaningful one — 221 documented sites, mostly Brownfields entries (121), the nearest Brownfields record about 0.7 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 Diablo Grande?
From about Nov 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 Dec 10 (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 10. Hardy greens and roots shrug off light frost and sweeten after it — leave them in.
Everything above is measured at Diablo Grande's scale — its 9b band and its 322-day season. Your yard writes its own version of Diablo Grande'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 Diablo Grande’s own scale
5 of the readings below were taken at Diablo Grande's own scale — the 2,751 acres it covers and 221 documented sites around it; 5 are borrowed from a wider read, named and linked below.
Measured here
- Diablo Grande's own USDA hardiness band, zones 9bUSDA PHZM 2023
- 221 documented contamination sites on the federal record near Diablo Grande, the closest Brownfields record about 0.7 miles out from the town centreFederal environmental registers
- Diablo Grande's boundary and the 2,751 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 9b and a ~322-day seasonGrowable Ground crop-matching engine
- Diablo Grande sits in the Central California Foothills and Coastal Mountains — not the ecoregion its county mostly readsUS EPA Level III Ecoregions
Inherited from a wider read
- The 28°F hard-freeze dates — Diablo Grande has no normal of its own, so its county's is the closest measured readfrom Stanislaus County
- Soil character — no town-scale survey exists, so Diablo Grande's 2,751 acres read through its county's SSURGO summaryfrom Stanislaus County
- Growing-degree days and winter chill — measured county-wide only, so the county page carries themfrom Stanislaus 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 Stanislaus County
What this page can’t tell you
- The soil pH, drainage, sun hours, and frost pockets on any one lot among Diablo Grande's 2,751 acreswhy one lot differs from the next →
- Which side of Diablo Grande you're on — a low spot frosts first and a south wall warms early, and one normal is being asked to speak for all 2,751 acresreading your own microclimate →
- How close that record sits to YOUR lot — the closest Brownfields record about 0.7 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 Diablo Grande-wide figureread your own land →