Monte Rio, 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.
The conditions favor okra, meyer lemon, california poppy, and artichoke, among others — though every individual site edits that list with its own soil, sun, and drainage.
Even in Monte Rio, 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 Monte Rio 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 Monte Rio — soil, climate, flood, and parcel records. How we handle your address.
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Monte Rio — the short answer
Monte Rio, California: USDA zone 9b, about 323 days between hard freezes, across 1K acres of town.
- USDA zone
- 9b
- USDA PHZM 2023
- Last hard freeze (28°F)
- Jan 23
- Sonoma County normal — NOAA 1991–2020, nearest to this town
- First hard freeze (28°F)
- Dec 12
- Sonoma County normal — NOAA 1991–2020, nearest to this town
- Days between freezes
- ~323
- Sonoma County normal — NOAA 1991–2020, nearest to this town
- Town area
- 1K 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 Sonoma County’s — the closest measured record, labelled as such rather than passed off as local.
Hardiness Zone Range
Zone 9b is Monte Rio's average, not your lot's — a low corner or a tree line moves it. Against Monte Rio's 323-day season, see what your own ground reads.
Soil varies lot by lot — soil types explained.
What this means for growing in Monte Rio
Each reading below is measured for Monte Rio itself — here is what it means for a garden here, and the move an experienced grower makes about it.
Season length
From county recordsMonte Rio runs about 323 days between hard freezes (read from Sonoma County, the closest normal to Monte Rio) — 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
MeasuredMonte Rio 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 Monte Rio is in
Monte Rio sits in the Coast Range — EPA Level III, inside the wider Marine West Coast Forest. That is read at Monte Rio's own centroid, and it is not what its county reads: Sonoma 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 Monte Rio
Every plant below cleared Monte Rio's own zone 9b and its 323-day season. Each card opens that plant's California profile. How we score.
Is it too late to plant in Monte Rio?
Rarely: the season closes in stages, not all at once, and each stage has its crops. 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 23 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Dec 12 — 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 Monte Rio
Closest first, within ~10 miles of Monte Rio. Listing isn't leaking, and distance isn't exposure.
- 007N010W07D001MNitrate · 0.5 mi
- PACIFIC BELLBrownfields · 0.7 mi
- SONOMA COUNTY WASTE MANAGEMENT AGENCYBrownfields · 0.9 mi
- NOELS AUTOMOTIVE MONTE RIO SERVICEBrownfields · 1.0 mi
- BERRY'S SAW MILL INCBrownfields · 1.2 mi
- CASINI ENTERPRISES INCBrownfields · 1.5 mi
- SOCO WATER AGENCY - MAIN LIFTUnderground Storage Tanks · 1.5 mi
- HAYNES TRANSPORTATIONBrownfields · 1.5 mi
- NORTHWOOD RECREATION INCBrownfields · 1.6 mi
- BOHEMIAN CLUBBrownfields · 1.7 mi
- DANNY BOY INCBrownfields · 1.8 mi
- AltamontMining · 2.2 mi
6 more sites are on the record inside the same radius. See them on the map
Measured from Monte Rio'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 Monte Rio.
Total Sites
194
within ~10 miles of Monte Rio
Risk Level
Elevated
Highest-severity
2 Superfund sites (none NPL-listed)
Sources Checked
within ~10 miles of Monte Rio
Severity Distribution
within ~10 miles of Monte Rio
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around Monte Rio, two things run higher than the national average within ~10 miles of Monte Rio — Mining (39 sites) and Brownfields (102 sites). That's not a problem with your land — it's information about 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 Monte Rio
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 Monte Rio average
Your land is one point inside Monte Rio
Everything above resolves to Monte Rio as a whole — one PHZM band, read across 1K acres, with hard-freeze dates borrowed from Sonoma 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 Monte Rio Average
Monte Rio Average
- ●USDA Zones 9b, averaged across Monte Rio
- ●One soil character for all of Monte Rio
- ●Frost dates read at Monte Rio's scale: Jan 23 to Dec 12
YOUR Parcel
- ✓Your exact zone, not Monte Rio's 9b
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your specific parcel in Monte Rio
Pull a site-specific report for your exact address in Monte Rio, California — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Monte Rio averages can't show:
We read public map data around Monte Rio — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Monte Rio average
How we know this about Monte Rio
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 Sonoma 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 Monte Rio
When does frost risk typically end in Monte Rio?
The last hard freeze (28°F) in Monte Rio typically lands around Jan 23, 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 13.
When is the first frost in Monte Rio?
The first hard freeze (28°F) in Monte Rio typically arrives around Dec 12, per NOAA 1991–2020 climate normals — the point tender summer crops finish. Lighter frosts run ahead of it, near Nov 28, so the watching starts about Nov 12 — about 323 days after the spring freeze cleared.
How long is the growing season in Monte Rio?
Measured between 28°F hard freezes, Monte Rio sees about 323 frost-free days — roughly Jan 23 through Dec 12, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer Feb 13 to Nov 28, about 288 days.
Is the soil safe to grow vegetables in Monte Rio?
The federal record around Monte Rio is a meaningful one — 194 documented sites, mostly Brownfields entries (102), the nearest Nitrate record about 0.5 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 Monte Rio?
From about Nov 12 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 12 (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 12. Hardy greens and roots shrug off light frost and sweeten after it — leave them in.
Everything above is measured at Monte Rio's scale — its 9b band and its 323-day season. Your yard writes its own version of Monte Rio'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 Monte Rio’s own scale
5 of the readings below were taken at Monte Rio's own scale — the 1,219 acres it covers and 194 documented sites around it; 5 are borrowed from a wider read, named and linked below.
Measured here
- Monte Rio's own USDA hardiness band, zones 9bUSDA PHZM 2023
- 194 documented contamination sites on the federal record near Monte Rio, the closest Nitrate record about 0.5 miles out from the town centreFederal environmental registers
- Monte Rio's boundary and the 1,219 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 9b and a ~323-day seasonGrowable Ground crop-matching engine
- Monte Rio sits in the Coast Range — not the ecoregion its county mostly readsUS EPA Level III Ecoregions
Inherited from a wider read
- The 28°F hard-freeze dates — Monte Rio has no normal of its own, so its county's is the closest measured readfrom Sonoma County
- Soil character — no town-scale survey exists, so Monte Rio's 1,219 acres read through its county's SSURGO summaryfrom Sonoma County
- Growing-degree days and winter chill — measured county-wide only, so the county page carries themfrom Sonoma 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 Sonoma County
What this page can’t tell you
- The soil pH, drainage, sun hours, and frost pockets on any one lot among Monte Rio's 1,219 acreswhy one lot differs from the next →
- Which side of Monte Rio you're on — a low spot frosts first and a south wall warms early, and one normal is being asked to speak for all 1,219 acresreading your own microclimate →
- How close that record sits to YOUR lot — the closest Nitrate record about 0.5 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 Monte Rio-wide figureread your own land →
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