Columbia County, in Washington, sits in USDA hardiness zone 7a — enough range to grow cool-season vegetables, hardy fruit, and warm-season crops that mature before the first hard frost.
A short list that earns its place here — cabbage, pawpaw, california poppy, and collard greens — with any one site's soil, sun, and drainage making the final cut.
Columbia 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
Columbia County holds more than one microclimate.
Soils and elevations shift across Columbia 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 Columbia County — soil, climate, flood, and parcel records. How we handle your address.
No card required · your full report in seconds
Columbia County — the short answer
Columbia County, Washington: USDA zone 7a, about 202 days between hard freezes, across 556K acres.
- USDA zone
- 7a
- USDA PHZM 2023
- Last hard freeze (28°F)
- Apr 8
- NOAA 1991–2020 Climate Normals, 28°F
- First hard freeze (28°F)
- Oct 27
- NOAA 1991–2020 Climate Normals, 28°F
- Days between freezes
- ~202
- NOAA 1991–2020 Climate Normals, 28°F
- County area
- 556K 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 Columbia County's average, not your lot's — a low corner or a tree line moves it. Against Columbia County's 202-day season, see what your own ground reads.
Heat in Columbia County
Across a year, Columbia County accumulates about 2,069 growing degree days above 50°F, about 356 more than the middle Washington county — ahead of 32 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 Columbia County
Across Columbia County, the ground is predominantly Mollisols, where Athena, Walla Walla, and Limberjim are the most extensive named soil series. The soil is generally well drained with a silt loam surface. Topsoil pH runs about 6.5–7.2, neutral. Rainfall drains through hydrologic group C soils.
Soil order
Mollisols
Drainage
Well drained
Prime farmland
3%
Hydric soils
0%
Soil still varies lot by lot — soil types explained.
How the ground varies across Columbia County
The USDA soil survey maps 81% of Columbia County as well drained — but another 2% drains differently: 2% moderately well drained.
Athena is the most extensive named soil at 12% of mapped acres, then Walla Walla (12%) and Limberjim (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 Columbia County
Each reading below is measured for Columbia 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 Columbia 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 Columbia County runs about pH 6.5–7.2, 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
MeasuredColumbia County runs about 202 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
MeasuredColumbia 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 Columbia County is in
Columbia County spans 2 EPA Level III ecoregions — Columbia Plateau (62%) and Blue Mountains (39%). 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 Columbia County
We scored all 1,086 plants against Columbia County's own USDA zone 7a and its own 202-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 Columbia County?
Too late for some crops, right on time for others — a growing season is a sequence, not a deadline. Cool-season crops can go in from around Mar 11; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near Apr 8 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Oct 27 — long-season crops need about 90 days of runway, quick greens only 30. Here the season winds down slowly: late sowings, a real autumn harvest, and garlic in the ground before the first hard freeze.
Documented around Columbia County
- monarch butterfly2 documented records
Sighting records, so they follow observers as much as insects.
What gets applied to farmland in Columbia County
USGS estimates 87,180 lb of Glyphosate on Columbia County farmland in 2019, its largest by weight, ahead of Bromoxynil (22,122 lb) and Propiconazole (10,609 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 Columbia County — and how to grow with it.
We checked the federal record across Columbia County — 56 documented sites across 3 of the 9 source types we track.
The most significant on record: 5 brownfield sites. Former commercial or industrial land where legacy contamination may persist.
The federal record across Columbia County is a modest one — a typical footprint for a growing area. Nothing here calls for alarm; it's worth knowing which recorded sites sit closest to where you grow, and each one on the map carries its type and location. If one turns out to be a near neighbor, a one-time soil test settles the question.
Sources: EPA, USGS — 1.8M documented sites tracked nationwide across 9 federal source types.
What's on the federal record near Columbia County
Closest first, across Columbia County. Listing isn't leaking, and distance isn't exposure.
- GURNSEY STREET COUNTY SHOPUnderground Storage Tanks · 2.7 mi
- CARL ROWE JRUnderground Storage Tanks · 2.9 mi
- DAYTON GENERAL HOSPITALBrownfields · 3.1 mi
- COLUMBIA COUNTY HOSPITAL DISTRICTUnderground Storage Tanks · 3.1 mi
- BY LOW SELF SERVEUnderground Storage Tanks · 3.2 mi
- PENNER FARMS INCUnderground Storage Tanks · 3.2 mi
- LEWIS & CLARK TRAIL STATE PARKUnderground Storage Tanks · 3.2 mi
- GATEWAY SUPPLIESUnderground Storage Tanks · 3.2 mi
- DAYTON WA LINE SEG 450 PRINT 384Underground Storage Tanks · 3.2 mi
- 10N/39E-30H01Nitrate · 3.5 mi
- COLUMBIA COUNTY SCHOOL DISTRICT 2Underground Storage Tanks · 3.5 mi
- GREEN GIANT PILLSBURY COUnderground Storage Tanks · 3.7 mi
6 more sites are on the record inside the same radius. See them on the map
Measured from Columbia 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 Columbia County.
Severity Distribution
across Columbia County
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around Columbia County, Underground Storage Tanks runs higher than the national average — 43 sites across Columbia County. That's not a problem with your land — it's information about it.
Underground Storage Tanks: Underground storage tanks are the single most common source of soil contamination near homes and gardens.
Use raised beds with imported soil — this eliminates the primary soil-contact pathway.
Check your specific parcel in Columbia 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 Columbia County average
Your land is one point inside Columbia County
Everything above resolves to Columbia County as a whole — one PHZM band and one county frost record, read across 556K 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 Columbia County Average
Columbia County Average
- ●USDA Zones 7a, averaged across Columbia County
- ●One soil character for all of Columbia County
- ●Frost dates read at Columbia County's scale: Apr 8 to Oct 27
YOUR Parcel
- ✓Your exact zone, not Columbia County's 7a
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your parcel in Columbia County
Pull a site-specific report for your exact address in Columbia County, Washington — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Columbia County averages can't show:
We read public map data around Columbia County — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Columbia County average
How we know this about Columbia 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 Columbia County carries no record of its own, the figure is inherited and labelled — the resolution ledger below names each.
Common questions about Columbia County
When does frost risk typically end in Columbia County?
The last hard freeze (28°F) in Columbia County typically lands around Apr 8, 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 29.
How long is the growing season in Columbia County?
Measured between 28°F hard freezes, Columbia County sees about 202 frost-free days — roughly Apr 8 through Oct 27, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer Apr 29 to Oct 13, about 167 days.
Is the soil safe to grow vegetables in Columbia County?
The federal record around Columbia County shows 56 documented sites, mostly Underground Storage Tanks entries (43), the nearest Underground Storage Tanks record about 2.7 miles out — a typical footprint for a growing area, and proximity to a documented site is information, not a diagnosis of any one yard. It's worth seeing which recorded sites sit closest to where you grow, and testing the soil before new food beds near any of them.
Everything above is measured at Columbia County's scale — its 7a band and its 202-day season. Your yard writes its own version of Columbia 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 Columbia County’s own scale
9 of the readings below were taken at Columbia County's own scale — its own ~202-day span between 28°F freezes, the 3 most extensive soil series mapped here and 56 documented sites inside its boundary; one is borrowed from a wider read, named and linked below.
Measured here
- Columbia County's own USDA hardiness band, zones 7aUSDA PHZM 2023
- Columbia County's own 28°F hard-freeze dates and its ~202-day span between themNOAA 1991–2020 Climate Normals
- The soil order, drainage, surface pH, and the 3 most extensive named soil series mapped in Columbia CountyUSDA NRCS SSURGO
- 56 documented contamination sites inside the county boundary, distance-sorted from its center — the closest Underground Storage Tanks record about 2.7 miles outFederal environmental registers
- Columbia County's boundary and the 555,894 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 7a and a ~202-day seasonGrowable Ground crop-matching engine
- The 2 ecoregions Columbia County spans, Columbia Plateau the largestUS EPA Level III Ecoregions
- Open occurrence records documented in Columbia County for a tracked speciesGBIF derived datasets (CC0 / CC BY 4.0)
- Which agricultural compounds go onto Columbia 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 Columbia County — the ~202 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 Columbia County's 555,894 acreswhy one lot differs from the next →
- Which of those 56 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 Columbia Countyread your own land →