Prairie County, in Montana, sits in USDA hardiness zone 4a — a band that supports both cool-season staples and warm-season crops chosen to fit the local frost window.
Reliable performers under these conditions include cabbage, cranberry, turkish rocket, and collard greens; what your own ground favors still comes down to its soil, sun, and drainage.
Prairie County lies within the Yellowstone Valley — a regional growing area with its own character.
Grounded in USDA PHZM 2023 · Growable Ground suitability scoring · NOAA 1991–2020 Climate Normals
Prairie County holds more than one microclimate.
Soils and elevations shift across Prairie 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 Prairie County — soil, climate, flood, and parcel records. How we handle your address.
No card required · your full report in seconds
Prairie County — the short answer
Prairie County, Montana: USDA zone 4a, about 158 days between hard freezes, across 1.1M acres.
- USDA zone
- 4a
- USDA PHZM 2023
- Last hard freeze (28°F)
- May 2
- NOAA 1991–2020 Climate Normals, 28°F
- First hard freeze (28°F)
- Oct 7
- NOAA 1991–2020 Climate Normals, 28°F
- Days between freezes
- ~158
- NOAA 1991–2020 Climate Normals, 28°F
- County area
- 1.1M 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 4a is Prairie County's average, not your lot's — a low corner or a tree line moves it. Against Prairie County's 158-day season, see what your own ground reads.
Heat in Prairie County
Across a year, Prairie County accumulates about 2,152 growing degree days above 50°F, about 482 more than the middle Montana county — ahead of 52 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 Prairie County
Across Prairie County, the ground is predominantly Inceptisols, where Lonna, Cambeth, and Cabbart are the most extensive named soil series. The soil is generally well drained with a silt loam surface. Topsoil pH runs about 7.5–7.9, slightly alkaline. Rainfall drains through hydrologic group C soils.
Soil order
Inceptisols
Drainage
Well drained
Hydric soils
0%
Soil still varies lot by lot — soil types explained.
How the ground varies across Prairie County
The USDA soil survey maps 89% of Prairie County as well drained — but another 4% drains differently: 3% somewhat excessively drained, 1% excessively drained.
Lonna is the most extensive named soil at 23% of mapped acres, then Cambeth (14%) and Cabbart (11%).
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 Prairie County
Each reading below is measured for Prairie 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 Prairie 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 Prairie County runs about pH 7.5–7.9, 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
MeasuredPrairie County runs about 158 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
MeasuredPrairie County sits in USDA hardiness zone 4a.
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 Prairie County is in
Prairie County sits in the Northwestern Great Plains — EPA Level III, inside the wider Great Plains. One consistent ecological setting across the whole county.
What Grows in Prairie County
We scored all 1,086 plants against Prairie County's own USDA zone 4a and its own 158-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 Prairie 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 4; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near May 2 (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. As the window narrows, the plantings just get faster — fall brassicas, then greens, then garlic to finish.
Documented around Prairie County
- monarch butterfly1 documented records
Sighting records, so they follow observers as much as insects.
What gets applied to farmland in Prairie County
USGS estimates 41,248 lb of Glyphosate on Prairie County farmland in 2019, its largest by weight, ahead of 2,4-d (8,834 lb) and Metolachlor & Metolachlor-s (8,241 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 Prairie County — and how to grow with it.
We checked the federal record across Prairie County — 85 documented sites across 3 of the 9 source types we track.
The most significant on record: 6 concentrated animal feeding operations. Large-scale animal operations that can contaminate soil and groundwater with nitrates and pathogens.
The federal record across Prairie 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 Prairie County
Closest first, across Prairie County. Listing isn't leaking, and distance isn't exposure.
- 13N49E18DBAD01Nitrate · 5.5 mi
- 11N50E03BC 01Nitrate · 6.2 mi
- 12N50E24CACD01Nitrate · 6.4 mi
- 11N50E08DD 01Nitrate · 7.0 mi
- 13N50E10CDDC01Nitrate · 8.0 mi
- HARDING LAND AND CATTLE CO INCCAFO · 8.1 mi
- HOMESTEAD CATTLE CO LLCCAFO · 8.2 mi
- BUFFALO RAPIDS IRRIGATION PROJECTUnderground Storage Tanks · 8.7 mi
- FORMER MWRR TERRYUnderground Storage Tanks · 8.7 mi
- J RANCH INCUnderground Storage Tanks · 8.7 mi
- CHERRY CREEK RANCHUnderground Storage Tanks · 8.7 mi
- RAYMOND STRASHEIMUnderground Storage Tanks · 8.7 mi
6 more sites are on the record inside the same radius. See them on the map
Measured from Prairie 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 Prairie County.
Total Sites
85
across Prairie County
Risk Level
Moderate
Highest-severity
6 concentrated animal feeding operations
Sources Checked
across Prairie County
Severity Distribution
across Prairie County
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around Prairie County, two things run higher than the national average across Prairie County — CAFO (6 sites) and Nitrate (58 sites). That's not a problem with your land — it's information about it.
CAFO: CAFOs pose a different contamination profile than chemical sources.
Nitrate: Nitrate contamination primarily comes from agricultural fertilizer runoff and failing septic systems.
Wash all produce consumed raw thoroughly, especially leafy greens grown near CAFOs.
Test well water for nitrate if you rely on a private well for irrigation (EPA standard: 10 mg/L).
Check your specific parcel in Prairie 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 Prairie County average
Your land is one point inside Prairie County
Everything above resolves to Prairie County as a whole — one PHZM band and one county frost record, read across 1.1M 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 Prairie County Average
Prairie County Average
- ●USDA Zones 4a, averaged across Prairie County
- ●One soil character for all of Prairie County
- ●Frost dates read at Prairie County's scale: May 2 to Oct 7
YOUR Parcel
- ✓Your exact zone, not Prairie County's 4a
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your parcel in Prairie County
Pull a site-specific report for your exact address in Prairie County, Montana — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Prairie County averages can't show:
We read public map data around Prairie County — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Prairie County average
How we know this about Prairie 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 Prairie County carries no record of its own, the figure is inherited and labelled — the resolution ledger below names each.
Common questions about Prairie County
When does frost risk typically end in Prairie County?
The last hard freeze (28°F) in Prairie County typically lands around May 2, 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 23.
How long is the growing season in Prairie County?
Measured between 28°F hard freezes, Prairie County sees about 158 frost-free days — roughly May 2 through Oct 7, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer May 23 to Sep 23, about 123 days.
Is the soil safe to grow vegetables in Prairie County?
The federal record around Prairie County shows 85 documented sites, mostly Nitrate entries (58), the nearest Nitrate record about 5.5 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 Prairie County's scale — its 4a band and its 158-day season. Your yard writes its own version of Prairie 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 Prairie County’s own scale
9 of the readings below were taken at Prairie County's own scale — its own ~158-day span between 28°F freezes, the 3 most extensive soil series mapped here and 85 documented sites inside its boundary; one is borrowed from a wider read, named and linked below.
Measured here
- Prairie County's own USDA hardiness band, zones 4aUSDA PHZM 2023
- Prairie County's own 28°F hard-freeze dates and its ~158-day span between themNOAA 1991–2020 Climate Normals
- The soil order, drainage, surface pH, and the 3 most extensive named soil series mapped in Prairie CountyUSDA NRCS SSURGO
- 85 documented contamination sites inside the county boundary, distance-sorted from its center — the closest Nitrate record about 5.5 miles outFederal environmental registers
- Prairie County's boundary and the 1,111,425 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 4a and a ~158-day seasonGrowable Ground crop-matching engine
- Prairie County sitting wholly inside the Northwestern Great PlainsUS EPA Level III Ecoregions
- Open occurrence records documented in Prairie County for a tracked speciesGBIF derived datasets (CC0 / CC BY 4.0)
- Which agricultural compounds go onto Prairie 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 Prairie County — the ~158 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 Prairie County's 1,111,425 acreswhy one lot differs from the next →
- Which of those 85 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 Prairie Countyread your own land →