Rialto, California, sits in USDA hardiness zone 10a — a band that supports both cool-season staples and warm-season crops chosen to fit the local frost window.
These conditions suit avocado, meyer lemon, tomato, and artichoke — a starting list any specific site will trim or extend with its own soil, sun, and drainage.
Even in Rialto, 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 Rialto 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 Rialto — soil, climate, flood, and parcel records. How we handle your address.
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Rialto — the short answer
Rialto, California: USDA zone 10a, about 328 days between hard freezes, across 15K acres of city.
- USDA zone
- 10a
- USDA PHZM 2023
- Last hard freeze (28°F)
- Jan 18
- San Bernardino County normal — NOAA 1991–2020, nearest to this town
- First hard freeze (28°F)
- Dec 12
- San Bernardino County normal — NOAA 1991–2020, nearest to this town
- Days between freezes
- ~328
- San Bernardino County normal — NOAA 1991–2020, nearest to this town
- City area
- 15K 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 San Bernardino County’s — the closest measured record, labelled as such rather than passed off as local.
Hardiness Zone Range
Zone 10a is Rialto's average, not your lot's — a low corner or a tree line moves it. Against Rialto's 328-day season, see what your own ground reads.
Soil varies lot by lot — soil types explained.
What this means for growing in Rialto
Each reading below is measured for Rialto itself — here is what it means for a garden here, and the move an experienced grower makes about it.
Season length
From county recordsRialto runs about 328 days between hard freezes (read from San Bernardino County, the closest normal to Rialto) — 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
MeasuredRialto sits in USDA hardiness zone 10a.
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 Rialto is in
Rialto sits in the Southern California/Northern Baja Coast — EPA Level III, inside the wider Mediterranean California. That is read at Rialto's own centroid, and it is not what its county reads: San Bernardino County is mostly Mojave Basin and Range. The wider page above you is answering a different question about different ground.
What Grows in Rialto
Plants matched to Rialto's USDA zones 10a, 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 Rialto?
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 18 (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 Rialto
Closest first, within ~10 miles of Rialto. Listing isn't leaking, and distance isn't exposure.
- RIALTO UNIFIED SCHOOL DISTRICT - DOLLAHAN ELEMENTARYBrownfields · 1400 ft
- 001S005W03A002SNitrate · 1500 ft
- WEST VALLEY WATER DISTRICTBrownfields · 1500 ft
- JORGE CASTILLO DBA JAC TRUCKINGBrownfields · 1600 ft
- R. GUERRERO TRANSPORT INCBrownfields · 1700 ft
- 001S005W03A006SNitrate · 1800 ft
- 001S005W03A004SNitrate · 1800 ft
- 001S005W03A005SNitrate · 1800 ft
- 001S005W03A003SNitrate · 1800 ft
- 001S005W03A007SNitrate · 1800 ft
- A-QUALITY AUTO SERVICEBrownfields · 2300 ft
- 7-Eleven Inc #35348Underground Storage Tanks · 2400 ft
6 more sites are on the record inside the same radius. See them on the map
Measured from Rialto'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 Rialto.
Sources Checked
within ~10 miles of Rialto
Severity Distribution
within ~10 miles of Rialto
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around Rialto, Brownfields runs higher than the national average — 4,604 sites within ~10 miles of Rialto. 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.
Check EPA brownfield remediation status — many sites have completed cleanup with institutional controls.
Check your specific parcel in Rialto
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 Rialto average
Your land is one point inside Rialto
Everything above resolves to Rialto as a whole — one PHZM band, read across 15K acres, with hard-freeze dates borrowed from San Bernardino County’s record because no 30-year normal resolves at this city’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 city 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 Rialto Average
Rialto Average
- ●USDA Zones 10a, averaged across Rialto
- ●One soil character for all of Rialto
- ●Frost dates read at Rialto's scale: Jan 18 to Dec 12
YOUR Parcel
- ✓Your exact zone, not Rialto's 10a
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your specific parcel in Rialto
Pull a site-specific report for your exact address in Rialto, California — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Rialto averages can't show:
We read public map data around Rialto — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Rialto average
How we know this about Rialto
The datasets: hardiness from the USDA ARS Plant Hardiness Zone Map 2023, read at this city’s own centroid; hard-freeze dates from NOAA 1991–2020 28°F normals at San Bernardino 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 city grain anywhere on this page — there is no city-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 Rialto
When does frost risk typically end in Rialto?
The last hard freeze (28°F) in Rialto typically lands around Jan 18, 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 8.
When is the first frost in Rialto?
The first hard freeze (28°F) in Rialto 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 328 days after the spring freeze cleared.
How long is the growing season in Rialto?
Measured between 28°F hard freezes, Rialto sees about 328 frost-free days — roughly Jan 18 through Dec 12, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer Feb 8 to Nov 28, about 293 days.
Is the soil safe to grow vegetables in Rialto?
The federal record around Rialto runs heavier than most — 5,933 documented sites, mostly Brownfields entries (4,604), the nearest Brownfields record about 0.3 miles out — so test the soil before planting food in the ground, and raised beds with clean imported soil grow well in the meantime. Even here, proximity to a documented site is information, not a diagnosis of any one yard; the contamination map shows exactly what's recorded and where.
How do I protect my plants from frost in Rialto?
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 Rialto's scale — its 10a band and its 328-day season. Your yard writes its own version of Rialto'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 Rialto’s own scale
4 of the readings below were taken at Rialto's own scale — the 15,419 acres it covers and 5,933 documented sites around it; 6 are borrowed from a wider read, named and linked below.
Measured here
- Rialto's own USDA hardiness band, zones 10aUSDA PHZM 2023
- 5,933 documented contamination sites on the federal record near Rialto, the closest Brownfields record about 0.3 miles out from the town centreFederal environmental registers
- Rialto's boundary and the 15,419 acres inside itUS Census TIGER/Line 2025
- Rialto sits in the Southern California/Northern Baja Coast — not the ecoregion its county mostly readsUS EPA Level III Ecoregions
Inherited from a wider read
- The 28°F hard-freeze dates — Rialto has no normal of its own, so its county's is the closest measured readfrom San Bernardino County
- Soil character — no town-scale survey exists, so Rialto's 15,419 acres read through its county's SSURGO summaryfrom San Bernardino 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 San Bernardino 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 San Bernardino County
What this page can’t tell you
- The soil pH, drainage, sun hours, and frost pockets on any one lot among Rialto's 15,419 acreswhy one lot differs from the next →
- Which side of Rialto you're on — a low spot frosts first and a south wall warms early, and one normal is being asked to speak for all 15,419 acresreading your own microclimate →
- How close that record sits to YOUR lot — the closest Brownfields 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 Rialto-wide figureread your own land →
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