San Jose, Illinois, sits in USDA hardiness zone 6a — enough range to grow cool-season vegetables, hardy fruit, and warm-season crops that mature before the first hard frost.
The conditions favor cabbage, hazelnut, lavender, and collard greens, among others — though every individual site edits that list with its own soil, sun, and drainage.
Even in San Jose, 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 San Jose 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 San Jose — soil, climate, flood, and parcel records. How we handle your address.
No card required · your full report in seconds
San Jose — the short answer
San Jose, Illinois: USDA zone 6a, about 208 days between hard freezes, across 265 acres of town.
- USDA zone
- 6a
- USDA PHZM 2023
- Last hard freeze (28°F)
- Apr 5
- NOAA 1991–2020 Climate Normals, 28°F — this town
- First hard freeze (28°F)
- Oct 30
- NOAA 1991–2020 Climate Normals, 28°F — this town
- Days between freezes
- ~208
- NOAA 1991–2020 Climate Normals, 28°F — this town
- Town area
- 265 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 6a is San Jose's average, not your lot's — a low corner or a tree line moves it. Against San Jose's 208-day season, see what your own ground reads.
Soil varies lot by lot — soil types explained.
What this means for growing in San Jose
Each reading below is measured for San Jose itself — here is what it means for a garden here, and the move an experienced grower makes about it.
Season length
MeasuredSan Jose runs about 208 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
MeasuredSan Jose sits in USDA hardiness zone 6a.
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 San Jose is in
San Jose sits in the Central Corn Belt Plains — EPA Level III, inside the wider Eastern Temperate Forests. That is read at San Jose's own centroid rather than borrowed from Mason County.
What Grows in San Jose
Every plant below cleared San Jose's own zone 6a and its 208-day season. Each card opens that plant's Illinois profile. How we score.
Is it too late to plant in San Jose?
Usually not — gardeners here simply switch what goes in the ground as the season moves. Cool-season crops can go in from around Mar 8; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near Apr 5 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Oct 30 — long-season crops need about 90 days of runway, quick greens only 30. There is slack in a calendar like this — late plantings, second rounds of favorites, and a fall bench that keeps beds working.
What's on the federal record near San Jose
Closest first, within ~10 miles of San Jose. Listing isn't leaking, and distance isn't exposure.
- Shawgo LloydUnderground Storage Tanks · 200 ft
- Griffin Oil Co., Inc.Underground Storage Tanks · 250 ft
- BORDEN CHEMICAL SMITH-DOUGLASS DIVBrownfields · 650 ft
- Casey's General Store #1613Underground Storage Tanks · 700 ft
- Illini Central Unit 189Underground Storage Tanks · 900 ft
- Lemme Gina AUnderground Storage Tanks · 900 ft
- Yentes LarryUnderground Storage Tanks · 900 ft
- SAN JOSE AUTOBODYBrownfields · 1100 ft
- Allens Grove Twp Storage BldgUnderground Storage Tanks · 1100 ft
- Taloma Farmers Grain CoUnderground Storage Tanks · 1100 ft
- San Jose Fs IncUnderground Storage Tanks · 1600 ft
- Clark Donald RUnderground Storage Tanks · 1600 ft
6 more sites are on the record inside the same radius. See them on the map
Measured from San Jose'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 San Jose.
Total Sites
106
within ~10 miles of San Jose
Risk Level
Elevated
Highest-severity
1 Superfund site (none NPL-listed)
Sources Checked
within ~10 miles of San Jose
Severity Distribution
within ~10 miles of San Jose
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around San Jose, CAFO runs higher than the national average — 4 sites within ~10 miles of San Jose. That's not a problem with your land — it's information about it.
CAFO: CAFOs pose a different contamination profile than chemical sources.
Wash all produce consumed raw thoroughly, especially leafy greens grown near CAFOs.
Check your specific parcel in San Jose
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 San Jose average
Your land is one point inside San Jose
Everything above resolves to San Jose as a whole — one PHZM band and one 28°F frost record, read across 265 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 San Jose Average
San Jose Average
- ●USDA Zones 6a, averaged across San Jose
- ●One soil character for all of San Jose
- ●Frost dates read at San Jose's scale: Apr 5 to Oct 30
YOUR Parcel
- ✓Your exact zone, not San Jose's 6a
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your specific parcel in San Jose
Pull a site-specific report for your exact address in San Jose, Illinois — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that San Jose averages can't show:
We read public map data around San Jose — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the San Jose average
How we know this about San Jose
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 San Jose’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 San Jose
When does frost risk typically end in San Jose?
The last hard freeze (28°F) in San Jose typically lands around Apr 5, 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 Apr 26.
When is the first frost in San Jose?
The first hard freeze (28°F) in San Jose typically arrives around Oct 30, per NOAA 1991–2020 climate normals — the point tender summer crops finish. Lighter frosts run ahead of it, near Oct 16, so the watching starts about Sep 30 — about 208 days after the spring freeze cleared.
How long is the growing season in San Jose?
Measured between 28°F hard freezes, San Jose sees about 208 frost-free days — roughly Apr 5 through Oct 30, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer Apr 26 to Oct 16, about 173 days.
Is the soil safe to grow vegetables in San Jose?
The federal record around San Jose is a meaningful one — 106 documented sites, mostly Underground Storage Tanks entries (61), the nearest Underground Storage Tanks 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 San Jose?
From about Sep 30 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 Oct 30 (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 Oct 30. Hardy greens and roots shrug off light frost and sweeten after it — leave them in.
Everything above is measured at San Jose's scale — its 6a band and its 208-day season. Your yard writes its own version of San Jose'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 San Jose’s own scale
6 of the readings below were taken at San Jose's own scale — its own ~208-day season between 28°F freezes, the 265 acres it covers and 106 documented sites around it; 4 are borrowed from a wider read, named and linked below.
Measured here
- San Jose's own USDA hardiness band, zones 6aUSDA PHZM 2023
- San Jose's own 28°F hard-freeze dates, about Apr 5 and Oct 30 and the ~208-day span between themNOAA 1991–2020 Climate Normals
- 106 documented contamination sites on the federal record near San Jose, the closest Underground Storage Tanks record under a tenth of a mile out from the town centreFederal environmental registers
- San Jose's boundary and the 265 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 6a and a ~208-day seasonGrowable Ground crop-matching engine
- The ecoregion at San Jose's own centroid, the Central Corn Belt PlainsUS EPA Level III Ecoregions
Inherited from a wider read
- Soil character — no town-scale survey exists, so San Jose's 265 acres read through its county's SSURGO summaryfrom Mason County
- Growing-degree days and winter chill — measured county-wide only, so the county page carries themfrom Mason County
- The growing challenges every Illinois grower plans around — written at state scale, so they stay on the state guidefrom Illinois
- Butterfly and beetle records, and the farmland pesticide estimate — all published county-widefrom Mason County
What this page can’t tell you
- The soil pH, drainage, sun hours, and frost pockets on any one lot among San Jose's 265 acreswhy one lot differs from the next →
- Which side of San Jose you're on — a low spot frosts first and a south wall warms early, and one normal is being asked to speak for all 265 acresreading your own microclimate →
- How close that record sits to YOUR lot — the closest Underground Storage Tanks 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 San Jose-wide figureread your own land →
More in Illinois
Wider growing context
What grows across IllinoisSan Jose sits outside our named growing regions, so Illinois as a whole is its closest context here.
Nearby growing guides