Dewey County, in Oklahoma, 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.
Expect cabbage, hazelnut, california poppy, and collard greens to be strong candidates here; the deciding factors on any one parcel stay local — soil, sun, and drainage.
Grounded in USDA PHZM 2023 · Growable Ground suitability scoring · NOAA 1991–2020 Climate Normals
Dewey County holds more than one microclimate.
Soils and elevations shift across Dewey 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 Dewey County — soil, climate, flood, and parcel records. How we handle your address.
No card required · your full report in seconds
Dewey County — the short answer
Dewey County, Oklahoma: USDA zone 7a, about 228 days between hard freezes, across 640K acres.
- USDA zone
- 7a
- USDA PHZM 2023
- Last hard freeze (28°F)
- Mar 26
- NOAA 1991–2020 Climate Normals, 28°F
- First hard freeze (28°F)
- Nov 9
- NOAA 1991–2020 Climate Normals, 28°F
- Days between freezes
- ~228
- NOAA 1991–2020 Climate Normals, 28°F
- County area
- 640K 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 Dewey County's average, not your lot's — a low corner or a tree line moves it. Against Dewey County's 228-day season, see what your own ground reads.
Heat and winter chill in Dewey County
Across a year, Dewey County accumulates about 4,415 growing degree days above 50°F, about 305 fewer than the middle Oklahoma county — ahead of 11 of Oklahoma’s 77 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.
Winter banks about 2,281 hours below 45°F, 362 more than the Oklahoma middle of 1,919. Chill is what tells a fruit tree its dormancy is over, and it is set by climate rather than by anything you can build.
Grounded in PRISM Climate Group, Oregon State University — 1991–2020 monthly normals
Soil in Dewey County
Across Dewey County, the ground is predominantly Inceptisols, where Quinlan, Hardeman, and St. Paul are the most extensive named soil series. The soil is generally well drained with a loam surface. Topsoil pH runs about 7.2–7.9, slightly alkaline. Rainfall drains through hydrologic group A soils.
Soil order
Inceptisols
Drainage
Well drained
Prime farmland
38%
Hydric soils
1%
Soil still varies lot by lot — soil types explained.
How the ground varies across Dewey County
The USDA soil survey maps 88% of Dewey County as well drained — but another 11% drains differently: 8% somewhat excessively drained, 1% poorly drained.
Quinlan is the most extensive named soil at 23% of mapped acres, then Hardeman (12%) and St. Paul (10%).
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 Dewey County
Each reading below is measured for Dewey 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 Dewey County are well drained, in hydrologic group A — 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 Dewey County runs about pH 7.2–7.9, 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
MeasuredDewey County runs about 228 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
MeasuredDewey 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 Dewey County is in
Dewey County sits in the Central Great Plains — EPA Level III, inside the wider Great Plains. One consistent ecological setting across the whole county.
What Grows in Dewey County
We scored all 1,086 plants against Dewey County's own USDA zone 7a and its own 228-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 Oklahoma profile.
Is it too late to plant in Dewey County?
Usually not — gardeners here simply switch what goes in the ground as the season moves. Cool-season crops can go in from around Feb 26; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near Mar 26 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Nov 9 — 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.
What gets applied to farmland in Dewey County
USGS estimates 15,278 lb of 2,4-d on Dewey County farmland in 2019, its largest by weight, ahead of Glyphosate (14,525 lb) and Chlorpyrifos (4,154 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 Dewey County — and how to grow with it.
We checked the federal record across Dewey County — 110 documented sites across 6 of the 9 source types we track.
The most significant on record: 1 Toxics Release Inventory facility. Active industrial facilities reporting chemical releases to air, water, and land.
The federal record across Dewey 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 Dewey County
Closest first, across Dewey County. Listing isn't leaking, and distance isn't exposure.
- 17N-17W-08 CBB 1Nitrate · 2.4 mi
- Lenora Booster StationUnderground Storage Tanks · 2.7 mi
- Ne Trails Gas PlantUnderground Storage Tanks · 2.8 mi
- Anr Booster SiteUnderground Storage Tanks · 3.7 mi
- SMITH RANCHCAFO · 4.1 mi
- 18N-17W-24 BDD 1Nitrate · 4.1 mi
- 18N-17W-13 1Nitrate · 4.8 mi
- Taloga Public SchoolsUnderground Storage Tanks · 4.8 mi
- 18N-17W-09 AD 1Nitrate · 5.1 mi
- Taloga Short StopUnderground Storage Tanks · 5.1 mi
- Speer's 66 ServiceUnderground Storage Tanks · 5.2 mi
- Liston's Apco ServiceUnderground Storage Tanks · 5.2 mi
6 more sites are on the record inside the same radius. See them on the map
Measured from Dewey 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 Dewey County.
Total Sites
110
across Dewey County
Risk Level
Moderate
Highest-severity
1 Toxics Release Inventory facility
Sources Checked
across Dewey County
Severity Distribution
across Dewey County
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around Dewey County, Nitrate runs higher than the national average — 34 sites across Dewey County. Knowing it is half the work — and it's nothing a thoughtful grower can't plan for.
Nitrate: Nitrate contamination primarily comes from agricultural fertilizer runoff and failing septic systems.
Test well water for nitrate if you rely on a private well for irrigation (EPA standard: 10 mg/L).
Check your specific parcel in Dewey 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 Dewey County average
Your land is one point inside Dewey County
Everything above resolves to Dewey County as a whole — one PHZM band and one county frost record, read across 640K 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 Dewey County Average
Dewey County Average
- ●USDA Zones 7a, averaged across Dewey County
- ●One soil character for all of Dewey County
- ●Frost dates read at Dewey County's scale: Mar 26 to Nov 9
YOUR Parcel
- ✓Your exact zone, not Dewey County's 7a
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your parcel in Dewey County
Pull a site-specific report for your exact address in Dewey County, Oklahoma — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Dewey County averages can't show:
We read public map data around Dewey County — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Dewey County average
How we know this about Dewey 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 Dewey County carries no record of its own, the figure is inherited and labelled — the resolution ledger below names each.
Common questions about Dewey County
When does frost risk typically end in Dewey County?
The last hard freeze (28°F) in Dewey County typically lands around Mar 26, 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 16.
How long is the growing season in Dewey County?
Measured between 28°F hard freezes, Dewey County sees about 228 frost-free days — roughly Mar 26 through Nov 9, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer Apr 16 to Oct 26, about 193 days.
Is the soil safe to grow vegetables in Dewey County?
The federal record around Dewey County shows 110 documented sites, mostly Underground Storage Tanks entries (66), the nearest Nitrate record about 2.4 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 Dewey County's scale — its 7a band and its 228-day season. Your yard writes its own version of Dewey 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 Oklahoma's frost window, season length, and soil profile against the plant's real requirements.
What this page reads at Dewey County’s own scale
8 of the readings below were taken at Dewey County's own scale — its own ~228-day span between 28°F freezes, the 3 most extensive soil series mapped here and 110 documented sites inside its boundary; one is borrowed from a wider read, named and linked below.
Measured here
- Dewey County's own USDA hardiness band, zones 7aUSDA PHZM 2023
- Dewey County's own 28°F hard-freeze dates and its ~228-day span between themNOAA 1991–2020 Climate Normals
- The soil order, drainage, surface pH, and the 3 most extensive named soil series mapped in Dewey CountyUSDA NRCS SSURGO
- 110 documented contamination sites inside the county boundary, distance-sorted from its center — the closest Nitrate record about 2.4 miles outFederal environmental registers
- Dewey County's boundary and the 639,761 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 7a and a ~228-day seasonGrowable Ground crop-matching engine
- Dewey County sitting wholly inside the Central Great PlainsUS EPA Level III Ecoregions
- Which agricultural compounds go onto Dewey County farmland, and roughly how muchUSGS NAWQA EPest county estimates
Inherited from a wider read
- The growing challenges every Oklahoma grower plans around — written at state scale, so they stay on the state guidefrom Oklahoma
What this page can’t tell you
- How the season shifts across Dewey County — the ~228 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 Dewey County's 639,761 acreswhy one lot differs from the next →
- Which of those 110 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 Dewey Countyread your own land →