Jerome County, in Idaho, sits in USDA hardiness zone 6b — a zone band wide enough that plant choice, not possibility, is the interesting question.
Well-matched crops include cabbage, blackberry, california poppy, and collard greens, and the gap between "grows in the area" and "grows in your yard" is closed by soil, sun, and drainage.
Jerome County lies within the Magic Valley and the Snake River Plain — a regional growing area with its own character.
Grounded in USDA PHZM 2023 · Growable Ground suitability scoring · NOAA 1991–2020 Climate Normals
Jerome County holds more than one microclimate.
Soils and elevations shift across Jerome County, so your frost dates and drainage aren't the county average. 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 Jerome County — soil, climate, flood, and parcel records. How we handle your address.
No card required · your full report in seconds
Jerome County — the short answer
Jerome County, Idaho: USDA zone 6b, about 182 days between hard freezes, across 382K acres.
- USDA zone
- 6b
- USDA PHZM 2023
- Last hard freeze (28°F)
- Apr 21
- NOAA 1991–2020 Climate Normals, 28°F
- First hard freeze (28°F)
- Oct 20
- NOAA 1991–2020 Climate Normals, 28°F
- Days between freezes
- ~182
- NOAA 1991–2020 Climate Normals, 28°F
- County area
- 382K acres
- US Census TIGER/Line 2025
Every figure names the dataset it came from. Hard-freeze dates are county 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 6b is Jerome County's average, not your lot's — a low corner or a tree line moves it. Against Jerome County's 182-day season, see what your own ground reads.
Heat in Jerome County
Across a year, Jerome County accumulates about 2,237 growing degree days above 50°F, about 746 more than the middle Idaho county — ahead of 38 of Idaho’s 44 counties. Degree days are the heat a crop actually gets to work with — more of them is more room to ripen a long-season crop before the freeze closes the window.
Grounded in PRISM Climate Group, Oregon State University — 1991–2020 monthly normals
Soil in Jerome County
Across Jerome County, the ground is predominantly Aridisols, where Power, Portneuf, and Sluka are the most extensive named soil series. The soil is generally well drained with a silt loam surface. Topsoil pH runs about 7.0–7.5, neutral. Rainfall drains through hydrologic group C soils.
Soil order
Aridisols
Drainage
Well drained
Hydric soils
0%
Soil still varies lot by lot — soil types explained.
How the ground varies across Jerome County
The USDA soil survey maps 96% of Jerome County as well drained — but another 2% drains differently: 2% somewhat excessively drained.
Power is the most extensive named soil at 16% of mapped acres, then Portneuf (10%) and Sluka (9%).
Which of them your own lot sits on is a parcel question, not a county one. Check your address for the survey at your boundary.
What this means for growing in Jerome County
Each reading below is measured for Jerome County itself — here is what it means for a garden here, and the move an experienced grower makes about it.
Drainage
MeasuredThe dominant soils across Jerome County are well drained, in hydrologic group C — ground that drains quickly.
The upside is soil you can work early in spring and roots that never drown; the cost is that fast-draining ground dries out fast and leaches nutrients away before plants can use them.
Work in compost and mulch to hold moisture and feed, and water more often in short doses than deep and rarely.
USDA NRCS SSURGO
Surface pH
MeasuredTopsoil across Jerome County runs about pH 7.0–7.5, close to neutral.
This is the range most vegetables prefer — one correction you probably do not have to make, which is genuinely good news for a new bed.
Keep it there with compost rather than lime or sulfur, and only amend if your own soil test says otherwise.
USDA NRCS SSURGO
Season length
MeasuredJerome County runs about 182 days between hard freezes — a moderate growing season.
There is room for the full run of cool-season crops plus a warm-season main crop, but the calendar is tight enough that a late spring or early fall frost still decides how much finishes.
Time warm-season transplants to your last hard freeze, and a few weeks of season extension turns a near-miss harvest into a sure one.
NOAA 1991–2020 Climate Normals
Winter hardiness
MeasuredJerome County sits in USDA hardiness zone 6b.
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 Jerome County is in
Jerome County sits in the Snake River Plain — EPA Level III, inside the wider North American Deserts. One consistent ecological setting across the whole county.
What Grows in Jerome County
We scored all 1,086 plants against Jerome County's own USDA zone 6b and its own 182-day season between hard freezes, using the same matching engine that runs a full parcel report. These cleared both. Sun, soil pH and drainage vary lot by lot — those are the parcel questions below. Each card opens that plant's Idaho profile.
Is it too late to plant in Jerome County?
Almost never — the real question is what to plant next. Cool-season crops can go in from around Mar 24; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near Apr 21 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Oct 20 — long-season crops need about 90 days of runway, quick greens only 30. Even past midsummer there is room for a true fall garden here, and garlic planted near the close carries the momentum into next year.
Documented around Jerome County
- monarch butterfly1 documented records
Sighting records, so they follow observers as much as insects.
What gets applied to farmland in Jerome County
USGS estimates 59,871 lb of Glyphosate on Jerome County farmland in 2019, its largest by weight, ahead of Chlorpyrifos (11,685 lb) and Metribuzin (6,776 lb).
Farmland across the whole county, not any one lot. Check your address for the site-by-site record.
Safe to Grow Here?
What the federal record shows across Jerome County — and how to grow with it.
We checked the federal record across Jerome County — 381 documented sites across 8 of the 9 source types we track.
The most significant on record: 1 Superfund site (none NPL-listed). Sites tracked in EPA's Superfund program — from assessment-stage CERCLIS entries to confirmed National Priorities List cleanup sites.
There's a meaningful federal record across Jerome County — worth a look before you plant food, not a reason to hold back from growing. Proximity to a documented site is information, not a diagnosis of any one yard. A soil test before new food beds is the sensible precaution here, and the map shows exactly which sites sit where, so you can see what's actually near you.
Sources: EPA, USGS — 1.8M documented sites tracked nationwide across 9 federal source types.
What's on the federal record near Jerome County
Closest first, across Jerome County. Listing isn't leaking, and distance isn't exposure.
- 08S 19E 32DDC1Nitrate · 0.9 mi
- 09S 19E 08BAB1Nitrate · 1.9 mi
- 08S 18E 35AAC1Nitrate · 2.5 mi
- 08S 19E 34DAD1Nitrate · 2.7 mi
- 08S 19E 35CCC1Nitrate · 2.8 mi
- 08S 18E 35BACD1Nitrate · 2.9 mi
- 09S 18E 02BBC1 MV-50Nitrate · 3.4 mi
- 08S 19E 15DDD1-DESTROYEDNitrate · 3.4 mi
- 08S 19E 15DDD2Nitrate · 3.4 mi
- SUNDANCE RANCH INC.Underground Storage Tanks · 3.4 mi
- 08S 19E 35DDC1Nitrate · 3.5 mi
- 09S 18E 11CBC1 MV-51Nitrate · 4.1 mi
6 more sites are on the record inside the same radius. See them on the map
Measured from Jerome County'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 Jerome County.
Total Sites
381
across Jerome County
Risk Level
Elevated
Highest-severity
1 Superfund site (none NPL-listed)
Severity Distribution
across Jerome County
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around Jerome County, two things run higher than the national average across Jerome County — CAFO (20 sites) and Nitrate (238 sites). It's not cause for alarm — it's worth knowing, and there's a sensible way to grow around it.
CAFO: CAFOs pose a different contamination profile than chemical sources.
Nitrate: Nitrate contamination primarily comes from agricultural fertilizer runoff and failing septic systems.
Wash all produce consumed raw thoroughly, especially leafy greens grown near CAFOs.
Test well water for nitrate if you rely on a private well for irrigation (EPA standard: 10 mg/L).
Check your specific parcel in Jerome County
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 Jerome County average
Your land is one point inside Jerome County
Everything above resolves to Jerome County as a whole — one PHZM band and one county frost record, read across 382K 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 county 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 county average.
Your Lot vs the Jerome County Average
Jerome County Average
- ●USDA Zones 6b, averaged across Jerome County
- ●One soil character for all of Jerome County
- ●Frost dates read at Jerome County's scale: Apr 21 to Oct 20
YOUR Parcel
- ✓Your exact zone, not Jerome County's 6b
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your parcel in Jerome County
Pull a site-specific report for your exact address in Jerome County, Idaho — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Jerome County averages can't show:
We read public map data around Jerome County — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Jerome County average
How we know this about Jerome County
The datasets: hardiness from the USDA ARS Plant Hardiness Zone Map 2023, read at county grain; hard-freeze dates from NOAA 1991–2020 28°F normals at this county’s own record where one resolves, and the labelled statewide window where none does; soils from the USDA NRCS SSURGO survey, area-weighted across the county’s own map units; boundaries and acreage from US Census TIGER/Line 2025; the contamination and pesticide records from the federal sources named in their beats above. Where Jerome County carries no record of its own, the figure is inherited and labelled — the resolution ledger below names each.
Common questions about Jerome County
When does frost risk typically end in Jerome County?
The last hard freeze (28°F) in Jerome County typically lands around Apr 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 May 12.
How long is the growing season in Jerome County?
Measured between 28°F hard freezes, Jerome County sees about 182 frost-free days — roughly Apr 21 through Oct 20, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer May 12 to Oct 6, about 147 days.
Is the soil safe to grow vegetables in Jerome County?
The federal record around Jerome County is a meaningful one — 381 documented sites, mostly Nitrate entries (238), the nearest Nitrate record about 0.9 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.
Everything above is measured at Jerome County's scale — its 6b band and its 182-day season. Your yard writes its own version of Jerome County's numbers: we read soil, sun, drainage and frost at your exact address. Try it for 14 days — no card required.
Will It Grow Here?
Zone fit is the first question — each answer below reads Idaho's frost window, season length, and soil profile against the plant's real requirements.
What this page reads at Jerome County’s own scale
9 of the readings below were taken at Jerome County's own scale — its own ~182-day span between 28°F freezes, the 3 most extensive soil series mapped here and 381 documented sites inside its boundary; one is borrowed from a wider read, named and linked below.
Measured here
- Jerome County's own USDA hardiness band, zones 6bUSDA PHZM 2023
- Jerome County's own 28°F hard-freeze dates and its ~182-day span between themNOAA 1991–2020 Climate Normals
- The soil order, drainage, surface pH, and the 3 most extensive named soil series mapped in Jerome CountyUSDA NRCS SSURGO
- 381 documented contamination sites inside the county boundary, distance-sorted from its center — the closest Nitrate record about 0.9 miles outFederal environmental registers
- Jerome County's boundary and the 382,429 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 6b and a ~182-day seasonGrowable Ground crop-matching engine
- Jerome County sitting wholly inside the Snake River PlainUS EPA Level III Ecoregions
- Open occurrence records documented in Jerome County for a tracked speciesGBIF derived datasets (CC0 / CC BY 4.0)
- Which agricultural compounds go onto Jerome County farmland, and roughly how muchUSGS NAWQA EPest county estimates
Inherited from a wider read
- The growing challenges every Idaho grower plans around — written at state scale, so they stay on the state guidefrom Idaho
What this page can’t tell you
- How the season shifts across Jerome County — the ~182 days above is one reading at its centre; the 12 towns below each carry their owntowns in this county →
- The soil pH, drainage, sun hours, and frost pockets on any one lot among Jerome County's 382,429 acreswhy one lot differs from the next →
- Which of those 381 documented sites actually reaches your soil — that needs your address, the wind, and the groundwater directionhow we read the record →
- Where cold air settles, which slopes face the sun, and which way the wind runs on your own ground — none of it survives being averaged over Jerome Countyread your own land →