Adams County, in Washington, sits in USDA hardiness zone 7a — room for a real mix of vegetables, fruit, and perennials matched to the local frost calendar.
Reliable performers under these conditions include cabbage, pawpaw, california poppy, and collard greens; what your own ground favors still comes down to its soil, sun, and drainage.
Adams County lies within the Columbia Basin — a regional growing area with its own character.
Grounded in USDA PHZM 2023 · Growable Ground suitability scoring · NOAA 1991–2020 Climate Normals
Adams County holds more than one microclimate.
Soils and elevations shift across Adams 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 Adams County — soil, climate, flood, and parcel records. How we handle your address.
No card required · your full report in seconds
Adams County — the short answer
Adams County, Washington: USDA zone 7a, about 189 days between hard freezes, across 1.2M acres.
- USDA zone
- 7a
- USDA PHZM 2023
- Last hard freeze (28°F)
- Apr 18
- NOAA 1991–2020 Climate Normals, 28°F
- First hard freeze (28°F)
- Oct 24
- NOAA 1991–2020 Climate Normals, 28°F
- Days between freezes
- ~189
- NOAA 1991–2020 Climate Normals, 28°F
- County area
- 1.2M 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 7a is Adams County's average, not your lot's — a low corner or a tree line moves it. Against Adams County's 189-day season, see what your own ground reads.
Heat in Adams County
Across a year, Adams County accumulates about 2,152 growing degree days above 50°F, about 439 more than the middle Washington county — ahead of 33 of Washington’s 39 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 Adams County
Across Adams County, the ground is predominantly Mollisols, where Shano, Ritzville, and Benge are the most extensive named soil series. The soil is generally well drained with a silt loam surface. Topsoil pH runs about 7.2–7.6, slightly alkaline. Rainfall drains through hydrologic group B soils.
Soil order
Mollisols
Drainage
Well drained
Hydric soils
1%
Soil still varies lot by lot — soil types explained.
How the ground varies across Adams County
The USDA soil survey maps 96% of Adams County as well drained — but another 2% drains differently: 1% somewhat poorly drained.
Shano is the most extensive named soil at 30% of mapped acres, then Ritzville (27%) and Benge (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 Adams County
Each reading below is measured for Adams 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 Adams 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 Adams County runs about pH 7.2–7.6, on the alkaline side.
Many vegetables cope, but acid-lovers like blueberries struggle, and iron and manganese lock up above about pH 7.5 — leaves yellow between the veins even in rich soil.
Elemental sulfur and generous organic matter lower pH slowly for the beds that need it; test first so you add only what the soil actually calls for.
USDA NRCS SSURGO
Season length
MeasuredAdams County runs about 189 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
MeasuredAdams County sits in USDA hardiness zone 7a.
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 Adams County is in
Adams County sits in the Columbia Plateau — EPA Level III, inside the wider North American Deserts. One consistent ecological setting across the whole county.
What Grows in Adams County
We scored all 1,086 plants against Adams County's own USDA zone 7a and its own 189-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 Washington profile.
Is it too late to plant in Adams County?
Usually not — gardeners here simply switch what goes in the ground as the season moves. Cool-season crops can go in from around Mar 21; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near Apr 18 (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 Adams County
- monarch butterfly1 documented records
Sighting records, so they follow observers as much as insects.
What gets applied to farmland in Adams County
USGS estimates 253,418 lb of Glyphosate on Adams County farmland in 2019, its largest by weight, ahead of 2,4-d (116,153 lb) and Bromoxynil (25,015 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 Adams County — and how to grow with it.
We checked the federal record across Adams County — 294 documented sites across 7 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 Adams 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 Adams County
Closest first, across Adams County. Listing isn't leaking, and distance isn't exposure.
- WSU DRY LAND RESEARCH UNITUnderground Storage Tanks · 2.6 mi
- RUDYS AVIATIONUnderground Storage Tanks · 4.6 mi
- RITZVILLE B53K021/RTVLWAQ2800Underground Storage Tanks · 4.8 mi
- LLOYD M BUTLERUnderground Storage Tanks · 5.5 mi
- UNION ELEVATOR AND WAREHOUSE COUnderground Storage Tanks · 5.5 mi
- SKIPS CHEVRONUnderground Storage Tanks · 5.6 mi
- ADAMS COUNTY MAINTENANCE SHOP LINDUnderground Storage Tanks · 5.7 mi
- ADAMS COUNTY FIRE DISTRICT 2Underground Storage Tanks · 5.7 mi
- MLJ PROPERTIES, LLCUnderground Storage Tanks · 5.8 mi
- RANCH PETROLEUM, INCUnderground Storage Tanks · 5.8 mi
- HELENA CHEMICAL CO LINDBrownfields · 5.9 mi
- LIND SCHOOL DISTRICTUnderground Storage Tanks · 6.0 mi
6 more sites are on the record inside the same radius. See them on the map
Measured from Adams 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 Adams County.
Total Sites
294
across Adams County
Risk Level
Elevated
Highest-severity
1 Superfund site (none NPL-listed)
Severity Distribution
across Adams County
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around Adams County, two things run higher than the national average across Adams County — Nitrate (84 sites) and Underground Storage Tanks (191 sites). It's not cause for alarm — it's worth knowing, and there's a sensible way to grow around it.
Nitrate: Nitrate contamination primarily comes from agricultural fertilizer runoff and failing septic systems.
Underground Storage Tanks: Underground storage tanks are the single most common source of soil contamination near homes and gardens.
Test well water for nitrate if you rely on a private well for irrigation (EPA standard: 10 mg/L).
Use raised beds with imported soil — this eliminates the primary soil-contact pathway.
Check your specific parcel in Adams 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 Adams County average
Your land is one point inside Adams County
Everything above resolves to Adams County as a whole — one PHZM band and one county frost record, read across 1.2M 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 Adams County Average
Adams County Average
- ●USDA Zones 7a, averaged across Adams County
- ●One soil character for all of Adams County
- ●Frost dates read at Adams County's scale: Apr 18 to Oct 24
YOUR Parcel
- ✓Your exact zone, not Adams County's 7a
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your parcel in Adams County
Pull a site-specific report for your exact address in Adams County, Washington — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Adams County averages can't show:
We read public map data around Adams County — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Adams County average
How we know this about Adams 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 Adams County carries no record of its own, the figure is inherited and labelled — the resolution ledger below names each.
Common questions about Adams County
When does frost risk typically end in Adams County?
The last hard freeze (28°F) in Adams County typically lands around Apr 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 May 9.
How long is the growing season in Adams County?
Measured between 28°F hard freezes, Adams County sees about 189 frost-free days — roughly Apr 18 through Oct 24, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer May 9 to Oct 10, about 154 days.
Is the soil safe to grow vegetables in Adams County?
The federal record around Adams County is a meaningful one — 294 documented sites, mostly Underground Storage Tanks entries (191), the nearest Underground Storage Tanks record about 2.6 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 Adams County's scale — its 7a band and its 189-day season. Your yard writes its own version of Adams 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 Washington's frost window, season length, and soil profile against the plant's real requirements.
What this page reads at Adams County’s own scale
9 of the readings below were taken at Adams County's own scale — its own ~189-day span between 28°F freezes, the 3 most extensive soil series mapped here and 294 documented sites inside its boundary; one is borrowed from a wider read, named and linked below.
Measured here
- Adams County's own USDA hardiness band, zones 7aUSDA PHZM 2023
- Adams County's own 28°F hard-freeze dates and its ~189-day span between themNOAA 1991–2020 Climate Normals
- The soil order, drainage, surface pH, and the 3 most extensive named soil series mapped in Adams CountyUSDA NRCS SSURGO
- 294 documented contamination sites inside the county boundary, distance-sorted from its center — the closest Underground Storage Tanks record about 2.6 miles outFederal environmental registers
- Adams County's boundary and the 1,231,992 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 7a and a ~189-day seasonGrowable Ground crop-matching engine
- Adams County sitting wholly inside the Columbia PlateauUS EPA Level III Ecoregions
- Open occurrence records documented in Adams County for a tracked speciesGBIF derived datasets (CC0 / CC BY 4.0)
- Which agricultural compounds go onto Adams County farmland, and roughly how muchUSGS NAWQA EPest county estimates
Inherited from a wider read
- The growing challenges every Washington grower plans around — written at state scale, so they stay on the state guidefrom Washington
What this page can’t tell you
- How the season shifts across Adams County — the ~189 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 Adams County's 1,231,992 acreswhy one lot differs from the next →
- Which of those 294 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 Adams Countyread your own land →