Niobrara County, in Wyoming, sits in USDA hardiness zone 5a — 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, cranberry, lavender, and collard greens — with any one site's soil, sun, and drainage making the final cut.
Grounded in USDA PHZM 2023 · Growable Ground suitability scoring · NOAA 1991–2020 Climate Normals
Niobrara County holds more than one microclimate.
Soils and elevations shift across Niobrara 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 Niobrara County — soil, climate, flood, and parcel records. How we handle your address.
No card required · your full report in seconds
Niobrara County — the short answer
Niobrara County, Wyoming: USDA zone 5a, about 155 days between hard freezes, across 1.7M acres.
- USDA zone
- 5a
- USDA PHZM 2023
- Last hard freeze (28°F)
- May 5
- NOAA 1991–2020 Climate Normals, 28°F
- First hard freeze (28°F)
- Oct 7
- NOAA 1991–2020 Climate Normals, 28°F
- Days between freezes
- ~155
- NOAA 1991–2020 Climate Normals, 28°F
- County area
- 1.7M 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 5a is Niobrara County's average, not your lot's — a low corner or a tree line moves it. Against Niobrara County's 155-day season, see what your own ground reads.
Heat in Niobrara County
Across a year, Niobrara County accumulates about 2,154 growing degree days above 50°F, about 280 more than the middle Wyoming county — ahead of 17 of Wyoming’s 23 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 Niobrara County
Across Niobrara County, the ground is predominantly Entisols, where Theedle, Kishona, and Shingle are the most extensive named soil series. The soil is generally well drained with a loam surface. Topsoil pH runs about 7.2–7.8, slightly alkaline. Rainfall drains through hydrologic group D soils.
Soil order
Entisols
Drainage
Well drained
Prime farmland
0%
Hydric soils
0%
Soil still varies lot by lot — soil types explained.
How the ground varies across Niobrara County
The USDA soil survey maps 95% of Niobrara County as well drained — but another 4% drains differently: 3% excessively drained, 2% somewhat excessively drained.
Theedle is the most extensive named soil at 13% of mapped acres, then Kishona (7%) and Shingle (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 Niobrara County
Each reading below is measured for Niobrara 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 Niobrara County are well drained, in hydrologic group D — 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 Niobrara County runs about pH 7.2–7.8, 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
MeasuredNiobrara County runs about 155 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
MeasuredNiobrara County sits in USDA hardiness zone 5a.
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 Niobrara County is in
Niobrara County spans 2 EPA Level III ecoregions — Northwestern Great Plains (70%) and High Plains (31%). 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 Niobrara County
We scored all 1,086 plants against Niobrara County's own USDA zone 5a and its own 155-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 Wyoming profile.
Is it too late to plant in Niobrara 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 Apr 7; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near May 5 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Oct 7 — 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 Niobrara County
USGS estimates 5,037 lb of Glyphosate on Niobrara County farmland in 2019, its largest by weight, ahead of 2,4-d (4,846 lb) and Chlorpyrifos (2,721 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 Niobrara County — and how to grow with it.
We checked the federal record across Niobrara County — 143 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 Niobrara 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 Niobrara County
Closest first, across Niobrara County. Listing isn't leaking, and distance isn't exposure.
- US FAA LUSK AFSFOBrownfields · 1.5 mi
- 35-064-02cc 01Nitrate · 3.1 mi
- 35-064-13ac 01Nitrate · 3.7 mi
- Mule Creek JunctionUnderground Storage Tanks · 3.8 mi
- 35-064-26cb 01Nitrate · 6.3 mi
- 35-062-15ac 01Nitrate · 9.8 mi
- WYOMING PIPELINE BUCK CREEK STATIONBrownfields · 10.7 mi
- 34-063-22aca01Nitrate · 10.9 mi
- Lance Creek FieldUnderground Storage Tanks · 11.6 mi
- 38-063-30cca01Nitrate · 12.0 mi
- 34-063-27cbd01Nitrate · 12.1 mi
- 34-065-04cb 01Nitrate · 12.9 mi
6 more sites are on the record inside the same radius. See them on the map
Measured from Niobrara 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 Niobrara County.
Total Sites
143
across Niobrara County
Risk Level
Moderate
Highest-severity
1 Toxics Release Inventory facility
Sources Checked
across Niobrara County
Severity Distribution
across Niobrara County
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around Niobrara County, Nitrate runs higher than the national average — 96 sites across Niobrara County. That's not a problem with your land — it's information about it.
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 Niobrara 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 Niobrara County average
Your land is one point inside Niobrara County
Everything above resolves to Niobrara County as a whole — one PHZM band and one county frost record, read across 1.7M 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 Niobrara County Average
Niobrara County Average
- ●USDA Zones 5a, averaged across Niobrara County
- ●One soil character for all of Niobrara County
- ●Frost dates read at Niobrara County's scale: May 5 to Oct 7
YOUR Parcel
- ✓Your exact zone, not Niobrara County's 5a
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your parcel in Niobrara County
Pull a site-specific report for your exact address in Niobrara County, Wyoming — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Niobrara County averages can't show:
We read public map data around Niobrara County — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Niobrara County average
How we know this about Niobrara 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 Niobrara County carries no record of its own, the figure is inherited and labelled — the resolution ledger below names each.
Common questions about Niobrara County
When does frost risk typically end in Niobrara County?
The last hard freeze (28°F) in Niobrara County typically lands around May 5, 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 26.
How long is the growing season in Niobrara County?
Measured between 28°F hard freezes, Niobrara County sees about 155 frost-free days — roughly May 5 through Oct 7, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer May 26 to Sep 23, about 120 days.
Is the soil safe to grow vegetables in Niobrara County?
The federal record around Niobrara County shows 143 documented sites, mostly Nitrate entries (96), the nearest Brownfields record about 1.5 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 Niobrara County's scale — its 5a band and its 155-day season. Your yard writes its own version of Niobrara 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 Wyoming's frost window, season length, and soil profile against the plant's real requirements.
What this page reads at Niobrara County’s own scale
8 of the readings below were taken at Niobrara County's own scale — its own ~155-day span between 28°F freezes, the 3 most extensive soil series mapped here and 143 documented sites inside its boundary; one is borrowed from a wider read, named and linked below.
Measured here
- Niobrara County's own USDA hardiness band, zones 5aUSDA PHZM 2023
- Niobrara County's own 28°F hard-freeze dates and its ~155-day span between themNOAA 1991–2020 Climate Normals
- The soil order, drainage, surface pH, and the 3 most extensive named soil series mapped in Niobrara CountyUSDA NRCS SSURGO
- 143 documented contamination sites inside the county boundary, distance-sorted from its center — the closest Brownfields record about 1.5 miles outFederal environmental registers
- Niobrara County's boundary and the 1,680,656 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 5a and a ~155-day seasonGrowable Ground crop-matching engine
- The 2 ecoregions Niobrara County spans, Northwestern Great Plains the largestUS EPA Level III Ecoregions
- Which agricultural compounds go onto Niobrara County farmland, and roughly how muchUSGS NAWQA EPest county estimates
Inherited from a wider read
- The growing challenges every Wyoming grower plans around — written at state scale, so they stay on the state guidefrom Wyoming
What this page can’t tell you
- How the season shifts across Niobrara County — the ~155 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 Niobrara County's 1,680,656 acreswhy one lot differs from the next →
- Which of those 143 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 Niobrara Countyread your own land →