Hilmar-Irwin, California, sits in USDA hardiness zone 9b — a range where zone-matched perennials and frost-aware annual timing set what succeeds.
Growers here do well with okra, meyer lemon, california poppy, and artichoke — with the usual caveat that any single yard's soil, sun, and drainage cast the deciding vote.
Even in Hilmar-Irwin, 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 Hilmar-Irwin 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 Hilmar-Irwin — soil, climate, flood, and parcel records. How we handle your address.
No card required · your full report in seconds
Hilmar-Irwin — the short answer
Hilmar-Irwin, California: USDA zone 9b, about 318 days between hard freezes, across 3K acres of town.
- USDA zone
- 9b
- USDA PHZM 2023
- Last hard freeze (28°F)
- Jan 21
- Merced County normal — NOAA 1991–2020, nearest to this town
- First hard freeze (28°F)
- Dec 5
- Merced County normal — NOAA 1991–2020, nearest to this town
- Days between freezes
- ~318
- Merced 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 Merced County’s — the closest measured record, labelled as such rather than passed off as local.
Hardiness Zone Range
Zone 9b is Hilmar-Irwin's average, not your lot's — a low corner or a tree line moves it. Against Hilmar-Irwin's 318-day season, see what your own ground reads.
Soil varies lot by lot — soil types explained.
What this means for growing in Hilmar-Irwin
Each reading below is measured for Hilmar-Irwin itself — here is what it means for a garden here, and the move an experienced grower makes about it.
Season length
From county recordsHilmar-Irwin runs about 318 days between hard freezes (read from Merced County, the closest normal to Hilmar-Irwin) — 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
MeasuredHilmar-Irwin 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 Hilmar-Irwin is in
Hilmar-Irwin sits in the Central California Valley — EPA Level III, inside the wider Mediterranean California. That is read at Hilmar-Irwin's own centroid rather than borrowed from Merced County.
What Grows in Hilmar-Irwin
Every plant below cleared Hilmar-Irwin's own zone 9b and its 318-day season. Each card opens that plant's California profile. How we score.
Is it too late to plant in Hilmar-Irwin?
For most of the year, no — what changes is which crops still fit the days remaining. 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 21 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Dec 5 — 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 Hilmar-Irwin
Closest first, within ~10 miles of Hilmar-Irwin. Listing isn't leaking, and distance isn't exposure.
- HILMAR ANIMAL HOSPITALBrownfields · 200 ft
- DOLLAR GENERAL #13400Brownfields · 250 ft
- CIRCLE KBrownfields · 450 ft
- Kings Food StoreUnderground Storage Tanks · 450 ft
- LIVINGSTON COMMUNITY HEALTH DBA HILMAR HEALTH CENTERBrownfields · 650 ft
- S & S BODY WORKSBrownfields · 950 ft
- VANCO REPAIR INCBrownfields · 950 ft
- Hilmar Unified School DistrictUnderground Storage Tanks · 950 ft
- HILMAR TOWN SVCBrownfields · 1100 ft
- HILMAR UNIFIEDBrownfields · 1100 ft
- SILVEIRA & SON DRYWALL INCBrownfields · 1200 ft
- HILMAR COUNTY WATER DISTRICTBrownfields · 1200 ft
6 more sites are on the record inside the same radius. See them on the map
Measured from Hilmar-Irwin'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 Hilmar-Irwin.
Sources Checked
within ~10 miles of Hilmar-Irwin
Severity Distribution
within ~10 miles of Hilmar-Irwin
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around Hilmar-Irwin, two things run higher than the national average within ~10 miles of Hilmar-Irwin — Brownfields (640 sites) and Nitrate (338 sites). That's not a problem with your land — it's information about it.
Brownfields: Brownfield sites are former commercial or industrial properties where legacy soil contamination (heavy metals, PAHs, petroleum compounds) may persist.
Nitrate: Nitrate contamination primarily comes from agricultural fertilizer runoff and failing septic systems.
Check EPA brownfield remediation status — many sites have completed cleanup with institutional controls.
Test well water for nitrate if you rely on a private well for irrigation (EPA standard: 10 mg/L).
Check your specific parcel in Hilmar-Irwin
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 Hilmar-Irwin average
Your land is one point inside Hilmar-Irwin
Everything above resolves to Hilmar-Irwin as a whole — one PHZM band, read across 3K acres, with hard-freeze dates borrowed from Merced 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 Hilmar-Irwin Average
Hilmar-Irwin Average
- ●USDA Zones 9b, averaged across Hilmar-Irwin
- ●One soil character for all of Hilmar-Irwin
- ●Frost dates read at Hilmar-Irwin's scale: Jan 21 to Dec 5
YOUR Parcel
- ✓Your exact zone, not Hilmar-Irwin's 9b
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your specific parcel in Hilmar-Irwin
Pull a site-specific report for your exact address in Hilmar-Irwin, California — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Hilmar-Irwin averages can't show:
We read public map data around Hilmar-Irwin — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Hilmar-Irwin average
How we know this about Hilmar-Irwin
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 Merced 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 Hilmar-Irwin
When does frost risk typically end in Hilmar-Irwin?
The last hard freeze (28°F) in Hilmar-Irwin typically lands around Jan 21, 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 11.
When is the first frost in Hilmar-Irwin?
The first hard freeze (28°F) in Hilmar-Irwin typically arrives around Dec 5, per NOAA 1991–2020 climate normals — the point tender summer crops finish. Lighter frosts run ahead of it, near Nov 21, so the watching starts about Nov 5 — about 318 days after the spring freeze cleared.
How long is the growing season in Hilmar-Irwin?
Measured between 28°F hard freezes, Hilmar-Irwin sees about 318 frost-free days — roughly Jan 21 through Dec 5, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer Feb 11 to Nov 21, about 283 days.
Is the soil safe to grow vegetables in Hilmar-Irwin?
The federal record around Hilmar-Irwin is a meaningful one — 1,071 documented sites, mostly Brownfields entries (640), the nearest Brownfields record under a tenth of a mile 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 Hilmar-Irwin?
From about Nov 5 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 5 (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 5. Hardy greens and roots shrug off light frost and sweeten after it — leave them in.
Everything above is measured at Hilmar-Irwin's scale — its 9b band and its 318-day season. Your yard writes its own version of Hilmar-Irwin'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 Hilmar-Irwin’s own scale
5 of the readings below were taken at Hilmar-Irwin's own scale — the 2,513 acres it covers and 1,071 documented sites around it; 5 are borrowed from a wider read, named and linked below.
Measured here
- Hilmar-Irwin's own USDA hardiness band, zones 9bUSDA PHZM 2023
- 1,071 documented contamination sites on the federal record near Hilmar-Irwin, the closest Brownfields record under a tenth of a mile out from the town centreFederal environmental registers
- Hilmar-Irwin's boundary and the 2,513 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 9b and a ~318-day seasonGrowable Ground crop-matching engine
- The ecoregion at Hilmar-Irwin's own centroid, the Central California ValleyUS EPA Level III Ecoregions
Inherited from a wider read
- The 28°F hard-freeze dates — Hilmar-Irwin has no normal of its own, so its county's is the closest measured readfrom Merced County
- Soil character — no town-scale survey exists, so Hilmar-Irwin's 2,513 acres read through its county's SSURGO summaryfrom Merced County
- Growing-degree days and winter chill — measured county-wide only, so the county page carries themfrom Merced 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 Merced County
What this page can’t tell you
- The soil pH, drainage, sun hours, and frost pockets on any one lot among Hilmar-Irwin's 2,513 acreswhy one lot differs from the next →
- Which side of Hilmar-Irwin you're on — a low spot frosts first and a south wall warms early, and one normal is being asked to speak for all 2,513 acresreading your own microclimate →
- How close that record sits to YOUR lot — the closest Brownfields record under a tenth of a mile 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 Hilmar-Irwin-wide figureread your own land →