Latah County, in Idaho, sits in USDA hardiness zone 6b — room for a real mix of vegetables, fruit, and perennials matched to the local frost calendar.
Crops well matched to these conditions include cabbage, blackberry, california poppy, and collard greens — though what thrives on any one site still turns on its specific soil, sun, and drainage.
Latah County lies within the Palouse — a regional growing area with its own character.
Grounded in USDA PHZM 2023 · Growable Ground suitability scoring · NOAA 1991–2020 Climate Normals
Latah County holds more than one microclimate.
Soils and elevations shift across Latah 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 Latah County — soil, climate, flood, and parcel records. How we handle your address.
No card required · your full report in seconds
Latah County — the short answer
Latah County, Idaho: USDA zone 6b, about 185 days between hard freezes, across 689K acres.
- USDA zone
- 6b
- USDA PHZM 2023
- Last hard freeze (28°F)
- Apr 22
- NOAA 1991–2020 Climate Normals, 28°F
- First hard freeze (28°F)
- Oct 24
- NOAA 1991–2020 Climate Normals, 28°F
- Days between freezes
- ~185
- NOAA 1991–2020 Climate Normals, 28°F
- County area
- 689K 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 Latah County's average, not your lot's — a low corner or a tree line moves it. Against Latah County's 185-day season, see what your own ground reads.
Heat in Latah County
Across a year, Latah County accumulates about 1,400 growing degree days above 50°F, about 91 fewer than the middle Idaho county — ahead of 18 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 Latah County
Across Latah County, the ground is predominantly Mollisols, where Santa, Southwick, and Taney are the most extensive named soil series. The soil is generally well drained with a ashy silt loam surface. Topsoil pH runs about 5.8–6.5, slightly acidic. Rainfall drains through hydrologic group B soils.
Soil order
Mollisols
Drainage
Well drained
Prime farmland
4%
Hydric soils
1%
Soil still varies lot by lot — soil types explained.
How the ground varies across Latah County
The USDA soil survey maps 57% of Latah County as well drained — but another 43% drains differently: 34% moderately well drained, 7% somewhat poorly drained.
Santa is the most extensive named soil at 9% of mapped acres, then Southwick (6%) and Taney (6%).
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 Latah County
Each reading below is measured for Latah 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 Latah County are well drained, in hydrologic group B — 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 Latah County runs about pH 5.8–6.5, 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
MeasuredLatah County runs about 185 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
MeasuredLatah 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 Latah County is in
Latah County spans 2 EPA Level III ecoregions — Northern Rockies (78%) and Columbia Plateau (22%). Which one your land falls in changes what grows wild there and how the ground behaves, and a county-wide answer cannot tell you which.
What Grows in Latah County
We scored all 1,086 plants against Latah County's own USDA zone 6b and its own 185-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 Latah County?
Almost never — the real question is what to plant next. Cool-season crops can go in from around Mar 25; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near Apr 22 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Oct 24 — long-season crops need about 90 days of runway, quick greens only 30. As the window narrows, the plantings just get faster — fall brassicas, then greens, then garlic to finish.
Documented around Latah County
- monarch butterfly2 documented records
Sighting records, so they follow observers as much as insects.
What gets applied to farmland in Latah County
USGS estimates 63,750 lb of Glyphosate on Latah County farmland in 2019, its largest by weight, ahead of Bromoxynil (28,425 lb) and 2,4-d (7,405 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 Latah County — and how to grow with it.
We checked the federal record across Latah County — 290 documented sites across 7 of the 9 source types we track.
The most significant on record: 2 Toxics Release Inventory facilities. Active industrial facilities reporting chemical releases to air, water, and land.
There's a meaningful federal record across Latah 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 Latah County
Closest first, across Latah County. Listing isn't leaking, and distance isn't exposure.
- 40N 03W 30ABA1Nitrate · 2.4 mi
- 40N 03W 28DDB1Nitrate · 3.0 mi
- LITTLER FARMUnderground Storage Tanks · 4.4 mi
- Mc Kinney ProspectMining · 4.8 mi
- ZIMMERMAN LOGGING CO.Underground Storage Tanks · 5.1 mi
- TROY COMPUTERS #1 & 2Underground Storage Tanks · 5.7 mi
- OMER DRURYUnderground Storage Tanks · 5.7 mi
- IDAHO CEDAR SALESUnderground Storage Tanks · 5.7 mi
- 39N 03W 07DAC1Nitrate · 5.9 mi
- 39N 03W 10CAB1Nitrate · 5.9 mi
- OWNBEY, WARREN - WARREN OWNBEY FEEDLOTCAFO · 5.9 mi
- STROM ELECTRICBrownfields · 6.0 mi
6 more sites are on the record inside the same radius. See them on the map
Measured from Latah 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 Latah County.
Total Sites
290
across Latah County
Risk Level
Elevated
Highest-severity
2 Toxics Release Inventory facilities
Severity Distribution
across Latah County
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around Latah County, two things run higher than the national average across Latah County — Mining (34 sites) and Nitrate (96 sites). Knowing it is half the work — and it's nothing a thoughtful grower can't plan for.
Mining: Mining sites — both historic and active — can leach heavy metals (arsenic, lead, cadmium, mercury) into soil and water for centuries after operations cease.
Nitrate: Nitrate contamination primarily comes from agricultural fertilizer runoff and failing septic systems.
Test soil for heavy metals (lead, arsenic, cadmium, mercury) — this is essential near any mining site.
Test well water for nitrate if you rely on a private well for irrigation (EPA standard: 10 mg/L).
Check your specific parcel in Latah 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 Latah County average
Your land is one point inside Latah County
Everything above resolves to Latah County as a whole — one PHZM band and one county frost record, read across 689K 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 Latah County Average
Latah County Average
- ●USDA Zones 6b, averaged across Latah County
- ●One soil character for all of Latah County
- ●Frost dates read at Latah County's scale: Apr 22 to Oct 24
YOUR Parcel
- ✓Your exact zone, not Latah County's 6b
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your parcel in Latah County
Pull a site-specific report for your exact address in Latah County, Idaho — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Latah County averages can't show:
We read public map data around Latah County — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Latah County average
How we know this about Latah 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 Latah County carries no record of its own, the figure is inherited and labelled — the resolution ledger below names each.
Common questions about Latah County
When does frost risk typically end in Latah County?
The last hard freeze (28°F) in Latah County typically lands around Apr 22, 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 13.
How long is the growing season in Latah County?
Measured between 28°F hard freezes, Latah County sees about 185 frost-free days — roughly Apr 22 through Oct 24, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer May 13 to Oct 10, about 150 days.
Is the soil safe to grow vegetables in Latah County?
The federal record around Latah County is a meaningful one — 290 documented sites, mostly Underground Storage Tanks entries (133), the nearest Nitrate record about 2.4 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 Latah County's scale — its 6b band and its 185-day season. Your yard writes its own version of Latah 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 Latah County’s own scale
9 of the readings below were taken at Latah County's own scale — its own ~185-day span between 28°F freezes, the 3 most extensive soil series mapped here and 290 documented sites inside its boundary; one is borrowed from a wider read, named and linked below.
Measured here
- Latah County's own USDA hardiness band, zones 6bUSDA PHZM 2023
- Latah County's own 28°F hard-freeze dates and its ~185-day span between themNOAA 1991–2020 Climate Normals
- The soil order, drainage, surface pH, and the 3 most extensive named soil series mapped in Latah CountyUSDA NRCS SSURGO
- 290 documented contamination sites inside the county boundary, distance-sorted from its center — the closest Nitrate record about 2.4 miles outFederal environmental registers
- Latah County's boundary and the 688,554 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 6b and a ~185-day seasonGrowable Ground crop-matching engine
- The 2 ecoregions Latah County spans, Northern Rockies the largestUS EPA Level III Ecoregions
- Open occurrence records documented in Latah County for a tracked speciesGBIF derived datasets (CC0 / CC BY 4.0)
- Which agricultural compounds go onto Latah 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 Latah County — the ~185 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 Latah County's 688,554 acreswhy one lot differs from the next →
- Which of those 290 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 Latah Countyread your own land →