Jefferson County, in Washington, sits in USDA hardiness zone 8a — enough range to grow cool-season vegetables, hardy fruit, and warm-season crops that mature before the first hard frost.
Reliable performers under these conditions include cabbage, fig, california poppy, and collard greens; what your own ground favors still comes down to its soil, sun, and drainage.
Jefferson County lies within the Olympic Peninsula and the Pacific Northwest — a regional growing area with its own character.
Grounded in USDA PHZM 2023 · Growable Ground suitability scoring · NOAA 1991–2020 Climate Normals
Jefferson County holds more than one microclimate.
Soils and elevations shift across Jefferson 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 Jefferson County — soil, climate, flood, and parcel records. How we handle your address.
No card required · your full report in seconds
Jefferson County — the short answer
Jefferson County, Washington: USDA zone 8a, about 187 days between hard freezes, across 1.2M acres.
- USDA zone
- 8a
- USDA PHZM 2023
- Last hard freeze (28°F)
- May 1
- NOAA 1991–2020 Climate Normals, 28°F
- First hard freeze (28°F)
- Nov 4
- NOAA 1991–2020 Climate Normals, 28°F
- Days between freezes
- ~187
- 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 8a is Jefferson County's average, not your lot's — a low corner or a tree line moves it. Against Jefferson County's 187-day season, see what your own ground reads.
Heat in Jefferson County
Across a year, Jefferson County accumulates about 603 growing degree days above 50°F, about 1,110 fewer than the middle Washington county — ahead of 1 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 Jefferson County
Across Jefferson County, the ground is predominantly Andisols, where Dimal, Hoko, and Solleks are the most extensive named soil series. The soil is generally well drained with a gravelly silt loam surface. Topsoil pH runs about 4.8–5.8, strongly acidic. Rainfall drains through hydrologic group B soils.
Soil order
Andisols
Drainage
Well drained
Prime farmland
6%
Hydric soils
4%
Soil still varies lot by lot — soil types explained.
How the ground varies across Jefferson County
The USDA soil survey maps 42% of Jefferson County as well drained — but another 52% drains differently: 34% moderately well drained, 13% somewhat excessively drained.
Dimal is the most extensive named soil at 10% of mapped acres, then Hoko (9%) and Solleks (7%).
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 Jefferson County
Each reading below is measured for Jefferson 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 Jefferson 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 Jefferson County runs about pH 4.8–5.8, on the acidic side.
Blueberries, potatoes, and rhododendrons thrive in it, but most vegetables start locking out nutrients below about pH 6.0 and grow pale and stunted no matter how much you feed them.
A measured lime application raises pH for the crops that need it — but test first, because the right rate depends on your own soil, not the county average.
USDA NRCS SSURGO
Season length
MeasuredJefferson County runs about 187 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
MeasuredJefferson County sits in USDA hardiness zone 8a.
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 Jefferson County is in
Jefferson County spans 3 EPA Level III ecoregions — Coast Range (64%), North Cascades (23%) and Puget Lowland (13%). 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 Jefferson County
We scored all 1,086 plants against Jefferson County's own USDA zone 8a and its own 187-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 Jefferson County?
Rarely: the season closes in stages, not all at once, and each stage has its crops. Cool-season crops can go in from around Apr 3; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near May 1 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Nov 4 — 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.
What gets applied to farmland in Jefferson County
USGS estimates 192 lb of 2,4-d on Jefferson County farmland in 2019, its largest by weight, ahead of Triclopyr (132 lb) and Glyphosate (106 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 Jefferson County — and how to grow with it.
We checked the federal record across Jefferson County — 171 documented sites across 8 of the 9 source types we track.
The most significant on record: 3 Superfund sites. 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 Jefferson 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 Jefferson County
Closest first, across Jefferson County. Listing isn't leaking, and distance isn't exposure.
- JEFFERSON COUNTY DISCOVERY BAYUnderground Storage Tanks · 17.1 mi
- DOSEWALLIPS STATE PARKUnderground Storage Tanks · 17.2 mi
- DOSEWALLIPS RANGER STATIONUnderground Storage Tanks · 18.9 mi
- Tubal Cain PropertyMining · 19.3 mi
- 26N/03W-15M01Nitrate · 22.6 mi
- Triple Ore Copper ProspectMining · 27.4 mi
- QUILCENE RANGER STATIONUnderground Storage Tanks · 28.0 mi
- 27N/02W-27B01Nitrate · 28.5 mi
- 27N/02W-22Q02Nitrate · 28.5 mi
- QUILCENE FISH HATCHERYUnderground Storage Tanks · 28.5 mi
- 27N/02W-22R01Nitrate · 28.7 mi
- OLYMPIC CORRECTIONS CENTERBrownfields · 29.0 mi
6 more sites are on the record inside the same radius. See them on the map
Measured from Jefferson 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 Jefferson County.
Sources Checked
across Jefferson County
Severity Distribution
across Jefferson County
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around Jefferson County, two things run higher than the national average across Jefferson County — PFAS (3 sites) and Superfund (3 sites). Knowing it is half the work — and it's nothing a thoughtful grower can't plan for.
PFAS: PFAS (per- and polyfluoroalkyl substances) are called "forever chemicals" because they do not biodegrade.
Superfund: Superfund sites represent the most severe contamination in the federal system.
Test irrigation water source — this is the primary pathway for PFAS to reach garden crops.
Commission professional soil testing before any food production (test for heavy metals, VOCs, and SVOCs).
Check your specific parcel in Jefferson 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 Jefferson County average
Your land is one point inside Jefferson County
Everything above resolves to Jefferson 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 Jefferson County Average
Jefferson County Average
- ●USDA Zones 8a, averaged across Jefferson County
- ●One soil character for all of Jefferson County
- ●Frost dates read at Jefferson County's scale: May 1 to Nov 4
YOUR Parcel
- ✓Your exact zone, not Jefferson County's 8a
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your parcel in Jefferson County
Pull a site-specific report for your exact address in Jefferson County, Washington — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Jefferson County averages can't show:
We read public map data around Jefferson County — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Jefferson County average
How we know this about Jefferson 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 Jefferson County carries no record of its own, the figure is inherited and labelled — the resolution ledger below names each.
Common questions about Jefferson County
When does frost risk typically end in Jefferson County?
The last hard freeze (28°F) in Jefferson County typically lands around May 1, 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 22.
How long is the growing season in Jefferson County?
Measured between 28°F hard freezes, Jefferson County sees about 187 frost-free days — roughly May 1 through Nov 4, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer May 22 to Oct 21, about 152 days.
Is the soil safe to grow vegetables in Jefferson County?
The federal record around Jefferson County is a meaningful one — 171 documented sites, mostly Underground Storage Tanks entries (123), the nearest Underground Storage Tanks record about 17 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 Jefferson County's scale — its 8a band and its 187-day season. Your yard writes its own version of Jefferson 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 Jefferson County’s own scale
8 of the readings below were taken at Jefferson County's own scale — its own ~187-day span between 28°F freezes, the 3 most extensive soil series mapped here and 171 documented sites inside its boundary; one is borrowed from a wider read, named and linked below.
Measured here
- Jefferson County's own USDA hardiness band, zones 8aUSDA PHZM 2023
- Jefferson County's own 28°F hard-freeze dates and its ~187-day span between themNOAA 1991–2020 Climate Normals
- The soil order, drainage, surface pH, and the 3 most extensive named soil series mapped in Jefferson CountyUSDA NRCS SSURGO
- 171 documented contamination sites inside the county boundary, distance-sorted from its center — the closest Underground Storage Tanks record about 17 miles outFederal environmental registers
- Jefferson County's boundary and the 1,154,385 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 8a and a ~187-day seasonGrowable Ground crop-matching engine
- The 3 ecoregions Jefferson County spans, Coast Range the largestUS EPA Level III Ecoregions
- Which agricultural compounds go onto Jefferson 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 Jefferson County — the ~187 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 Jefferson County's 1,154,385 acreswhy one lot differs from the next →
- Which of those 171 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 Jefferson Countyread your own land →