Big Horn County, in Montana, sits in USDA hardiness zone 4b — a zone band wide enough that plant choice, not possibility, is the interesting question.
On paper, cabbage, cranberry, turkish rocket, and collard greens all suit these conditions — on the ground, soil, sun, and drainage make the final call.
Grounded in USDA PHZM 2023 · Growable Ground suitability scoring · NOAA 1991–2020 Climate Normals
Big Horn County holds more than one microclimate.
Soils and elevations shift across Big Horn 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 Big Horn County — soil, climate, flood, and parcel records. How we handle your address.
No card required · your full report in seconds
Big Horn County — the short answer
Big Horn County, Montana: USDA zone 4b, about 155 days between hard freezes, across 3.2M acres.
- USDA zone
- 4b
- USDA PHZM 2023
- Last hard freeze (28°F)
- May 4
- NOAA 1991–2020 Climate Normals, 28°F
- First hard freeze (28°F)
- Oct 6
- NOAA 1991–2020 Climate Normals, 28°F
- Days between freezes
- ~155
- NOAA 1991–2020 Climate Normals, 28°F
- County area
- 3.2M 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 4b is Big Horn County's average, not your lot's — a low corner or a tree line moves it. Against Big Horn County's 155-day season, see what your own ground reads.
Heat in Big Horn County
Across a year, Big Horn County accumulates about 2,056 growing degree days above 50°F, about 386 more than the middle Montana county — ahead of 47 of Montana’s 56 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 Big Horn County
Across Big Horn County, the ground is predominantly Entisols, where Yamacall, Cabbart, and Midway 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 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 Big Horn County
The USDA soil survey maps 95% of Big Horn County as well drained — but another 2% drains differently: 1% moderately well drained, 1% excessively drained.
Yamacall is the most extensive named soil at 6% of mapped acres, then Cabbart (5%) and Midway (4%).
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 Big Horn County
Each reading below is measured for Big Horn 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 Big Horn 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 Big Horn 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
MeasuredBig Horn 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
MeasuredBig Horn County sits in USDA hardiness zone 4b.
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 Big Horn County is in
Big Horn County spans 2 EPA Level III ecoregions — Northwestern Great Plains (93%) and Middle Rockies (6%). 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 Big Horn County
We scored all 1,086 plants against Big Horn County's own USDA zone 4b 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 Montana profile.
Is it too late to plant in Big Horn County?
Usually not — gardeners here simply switch what goes in the ground as the season moves. Cool-season crops can go in from around Apr 6; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near May 4 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Oct 6 — long-season crops need about 90 days of runway, quick greens only 30. The tail of the season still works: sixty-day crops into late summer, quick greens after, garlic last of all.
Documented around Big Horn County
- monarch butterfly1 documented records
Sighting records, so they follow observers as much as insects.
What gets applied to farmland in Big Horn County
USGS estimates 343,055 lb of Glyphosate on Big Horn County farmland in 2019, its largest by weight, ahead of 2,4-d (162,047 lb) and Dicamba (19,145 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 Big Horn County — and how to grow with it.
We checked the federal record across Big Horn County — 1,017 documented sites across 7 of the 9 source types we track.
The most significant on record: 3 Superfund sites (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 Big Horn 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 Big Horn County
Closest first, across Big Horn County. Listing isn't leaking, and distance isn't exposure.
- 05S35E16AADC01Nitrate · 6.1 mi
- 04S35E33AC 01Nitrate · 6.2 mi
- 04S34E11DA 01Nitrate · 6.3 mi
- 05S35E03CC 01Nitrate · 6.4 mi
- 05S35E22CC 01Nitrate · 6.7 mi
- 04S35E21CD 02Nitrate · 6.7 mi
- 04S35E21CD 01Nitrate · 6.7 mi
- 05S35E27BA 01Nitrate · 7.0 mi
- 5S-35E-27bac01Nitrate · 7.1 mi
- 05S35E27DB 01Nitrate · 7.4 mi
- 05S35E34ABBB01Nitrate · 7.5 mi
- 04S35E16BD 01Nitrate · 7.6 mi
6 more sites are on the record inside the same radius. See them on the map
Measured from Big Horn 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 Big Horn County.
Total Sites
1,017
across Big Horn County
Risk Level
Elevated
Highest-severity
3 Superfund sites (none NPL-listed)
Sources Checked
across Big Horn County
Severity Distribution
across Big Horn County
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around Big Horn County, Nitrate runs higher than the national average — 890 sites across Big Horn 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 Big Horn 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 Big Horn County average
Your land is one point inside Big Horn County
Everything above resolves to Big Horn County as a whole — one PHZM band and one county frost record, read across 3.2M 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 Big Horn County Average
Big Horn County Average
- ●USDA Zones 4b, averaged across Big Horn County
- ●One soil character for all of Big Horn County
- ●Frost dates read at Big Horn County's scale: May 4 to Oct 6
YOUR Parcel
- ✓Your exact zone, not Big Horn County's 4b
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your parcel in Big Horn County
Pull a site-specific report for your exact address in Big Horn County, Montana — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Big Horn County averages can't show:
We read public map data around Big Horn County — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Big Horn County average
How we know this about Big Horn 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 Big Horn County carries no record of its own, the figure is inherited and labelled — the resolution ledger below names each.
Common questions about Big Horn County
When does frost risk typically end in Big Horn County?
The last hard freeze (28°F) in Big Horn County typically lands around May 4, 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 25.
How long is the growing season in Big Horn County?
Measured between 28°F hard freezes, Big Horn County sees about 155 frost-free days — roughly May 4 through Oct 6, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer May 25 to Sep 22, about 120 days.
Is the soil safe to grow vegetables in Big Horn County?
The federal record around Big Horn County is a meaningful one — 1,017 documented sites, mostly Nitrate entries (890), the nearest Nitrate record about 6.1 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 Big Horn County's scale — its 4b band and its 155-day season. Your yard writes its own version of Big Horn 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 Montana's frost window, season length, and soil profile against the plant's real requirements.
What this page reads at Big Horn County’s own scale
9 of the readings below were taken at Big Horn County's own scale — its own ~155-day span between 28°F freezes, the 3 most extensive soil series mapped here and 1,017 documented sites inside its boundary; one is borrowed from a wider read, named and linked below.
Measured here
- Big Horn County's own USDA hardiness band, zones 4bUSDA PHZM 2023
- Big Horn 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 Big Horn CountyUSDA NRCS SSURGO
- 1,017 documented contamination sites inside the county boundary, distance-sorted from its center — the closest Nitrate record about 6.1 miles outFederal environmental registers
- Big Horn County's boundary and the 3,198,575 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 4b and a ~155-day seasonGrowable Ground crop-matching engine
- The 2 ecoregions Big Horn County spans, Northwestern Great Plains the largestUS EPA Level III Ecoregions
- Open occurrence records documented in Big Horn County for a tracked speciesGBIF derived datasets (CC0 / CC BY 4.0)
- Which agricultural compounds go onto Big Horn County farmland, and roughly how muchUSGS NAWQA EPest county estimates
Inherited from a wider read
- The growing challenges every Montana grower plans around — written at state scale, so they stay on the state guidefrom Montana
What this page can’t tell you
- How the season shifts across Big Horn 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 Big Horn County's 3,198,575 acreswhy one lot differs from the next →
- Which of those 1,017 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 Big Horn Countyread your own land →