Roosevelt County, in Montana, sits in USDA hardiness zone 3b — enough range to grow cool-season vegetables, hardy fruit, and warm-season crops that mature before the first hard frost.
On paper, cabbage, cranberry, epazote, and collard greens all suit these conditions — on the ground, soil, sun, and drainage make the final call.
Roosevelt County lies within the Hi-Line — a regional growing area with its own character.
Grounded in USDA PHZM 2023 · Growable Ground suitability scoring · NOAA 1991–2020 Climate Normals
Roosevelt County holds more than one microclimate.
Soils and elevations shift across Roosevelt 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 Roosevelt County — soil, climate, flood, and parcel records. How we handle your address.
No card required · your full report in seconds
Roosevelt County — the short answer
Roosevelt County, Montana: USDA zone 3b, about 146 days between hard freezes, across 1.5M acres.
- USDA zone
- 3b
- USDA PHZM 2023
- Last hard freeze (28°F)
- May 7
- NOAA 1991–2020 Climate Normals, 28°F
- First hard freeze (28°F)
- Sep 30
- NOAA 1991–2020 Climate Normals, 28°F
- Days between freezes
- ~146
- NOAA 1991–2020 Climate Normals, 28°F
- County area
- 1.5M 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 3b is Roosevelt County's average, not your lot's — a low corner or a tree line moves it. Against Roosevelt County's 146-day season, see what your own ground reads.
Heat in Roosevelt County
Across a year, Roosevelt County accumulates about 1,899 growing degree days above 50°F, about 229 more than the middle Montana county — ahead of 35 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 Roosevelt County
Across Roosevelt County, the ground is predominantly Mollisols, where Zahill, Vida, and Dooley 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 C soils.
Soil order
Mollisols
Drainage
Well drained
Hydric soils
4%
Soil still varies lot by lot — soil types explained.
How the ground varies across Roosevelt County
The USDA soil survey maps 88% of Roosevelt County as well drained — but another 7% drains differently: 3% moderately well drained, 1% very poorly drained.
Zahill is the most extensive named soil at 26% of mapped acres, then Vida (16%) and Dooley (6%).
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 Roosevelt County
Each reading below is measured for Roosevelt 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 Roosevelt 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 Roosevelt 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
MeasuredRoosevelt County runs about 146 days between hard freezes — a short growing season.
Long-maturing crops like melons, sweet potatoes, and winter squash can run out of runway before the first hard freeze, ripening late or not at all.
Lead with fast-maturing varieties, and stretch the season on both ends with cold frames, low tunnels, or a greenhouse.
NOAA 1991–2020 Climate Normals
Winter hardiness
MeasuredRoosevelt County sits in USDA hardiness zone 3b.
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 Roosevelt County is in
Roosevelt County sits in the Northwestern Glaciated Plains — EPA Level III, inside the wider Great Plains. One consistent ecological setting across the whole county.
What Grows in Roosevelt County
We scored all 1,086 plants against Roosevelt County's own USDA zone 3b and its own 146-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 Roosevelt County?
For most of the year, no — what changes is which crops still fit the days remaining. Cool-season crops can go in from around Apr 9; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near May 7 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Sep 30 — long-season crops need about 90 days of runway, quick greens only 30. When the window is tight, the fall moves are quick ones — baby greens, radishes, and garlic set for next season.
What gets applied to farmland in Roosevelt County
USGS estimates 234,842 lb of Glyphosate on Roosevelt County farmland in 2019, its largest by weight, ahead of 2,4-d (52,746 lb) and Bromoxynil (11,610 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 Roosevelt County — and how to grow with it.
We checked the federal record across Roosevelt County — 441 documented sites across 5 of the 9 source types we track.
The most significant on record: 2 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 Roosevelt 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 Roosevelt County
Closest first, across Roosevelt County. Listing isn't leaking, and distance isn't exposure.
- 29N52E27DADC01 ROOSEVELT CO. 086Nitrate · 4.4 mi
- 29N51E09ABBA04 USGS93-1Nitrate · 4.4 mi
- 30N51E13DCBC01Nitrate · 4.8 mi
- 29N52E35CBBB02 CLEVELAND 086Nitrate · 5.1 mi
- MILO STANGLELAND JRUnderground Storage Tanks · 5.2 mi
- TREASURE STATE GRAIN INCUnderground Storage Tanks · 5.2 mi
- 28N53E06BBAB01 ROOSEVELT CO. 086Nitrate · 5.5 mi
- 29N51E34BC 01Nitrate · 5.6 mi
- 29N51E28DC 01Nitrate · 5.6 mi
- 29N51E34CC 01Nitrate · 6.0 mi
- 29N51E20DCDB01Nitrate · 6.0 mi
- 29N51E20CC 01Nitrate · 6.4 mi
6 more sites are on the record inside the same radius. See them on the map
Measured from Roosevelt 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 Roosevelt County.
Total Sites
441
across Roosevelt County
Risk Level
Elevated
Highest-severity
2 Superfund sites (none NPL-listed)
Sources Checked
across Roosevelt County
Severity Distribution
across Roosevelt County
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around Roosevelt County, Nitrate runs higher than the national average — 292 sites across Roosevelt 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 Roosevelt 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 Roosevelt County average
Your land is one point inside Roosevelt County
Everything above resolves to Roosevelt County as a whole — one PHZM band and one county frost record, read across 1.5M 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 Roosevelt County Average
Roosevelt County Average
- ●USDA Zones 3b, averaged across Roosevelt County
- ●One soil character for all of Roosevelt County
- ●Frost dates read at Roosevelt County's scale: May 7 to Sep 30
YOUR Parcel
- ✓Your exact zone, not Roosevelt County's 3b
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your parcel in Roosevelt County
Pull a site-specific report for your exact address in Roosevelt County, Montana — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Roosevelt County averages can't show:
We read public map data around Roosevelt County — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Roosevelt County average
How we know this about Roosevelt 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 Roosevelt County carries no record of its own, the figure is inherited and labelled — the resolution ledger below names each.
Common questions about Roosevelt County
When does frost risk typically end in Roosevelt County?
The last hard freeze (28°F) in Roosevelt County typically lands around May 7, 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 28.
How long is the growing season in Roosevelt County?
Measured between 28°F hard freezes, Roosevelt County sees about 146 frost-free days — roughly May 7 through Sep 30, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer May 28 to Sep 16, about 111 days.
Is the soil safe to grow vegetables in Roosevelt County?
The federal record around Roosevelt County is a meaningful one — 441 documented sites, mostly Nitrate entries (292), the nearest Nitrate record about 4.4 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.
How do gardeners stretch the season in Roosevelt County?
With about 146 frost-free days between hard freezes, Roosevelt County rewards the classic extension moves: floating row cover buys roughly two to four extra weeks at each shoulder — on this season that is a working window nearer 174 to 202 days — and cold frames or low tunnels buy more. Starting transplants indoors ahead of the May 7 hard-freeze normal stretches the season without touching the calendar.
Everything above is measured at Roosevelt County's scale — its 3b band and its 146-day season. Your yard writes its own version of Roosevelt 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 Roosevelt County’s own scale
8 of the readings below were taken at Roosevelt County's own scale — its own ~146-day span between 28°F freezes, the 3 most extensive soil series mapped here and 441 documented sites inside its boundary; one is borrowed from a wider read, named and linked below.
Measured here
- Roosevelt County's own USDA hardiness band, zones 3bUSDA PHZM 2023
- Roosevelt County's own 28°F hard-freeze dates and its ~146-day span between themNOAA 1991–2020 Climate Normals
- The soil order, drainage, surface pH, and the 3 most extensive named soil series mapped in Roosevelt CountyUSDA NRCS SSURGO
- 441 documented contamination sites inside the county boundary, distance-sorted from its center — the closest Nitrate record about 4.4 miles outFederal environmental registers
- Roosevelt County's boundary and the 1,506,944 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 3b and a ~146-day seasonGrowable Ground crop-matching engine
- Roosevelt County sitting wholly inside the Northwestern Glaciated PlainsUS EPA Level III Ecoregions
- Which agricultural compounds go onto Roosevelt 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 Roosevelt County — the ~146 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 Roosevelt County's 1,506,944 acreswhy one lot differs from the next →
- Which of those 441 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 Roosevelt Countyread your own land →