Mountrail County, in North Dakota, sits in USDA hardiness zone 4a — a range where zone-matched perennials and frost-aware annual timing set what succeeds.
Growers here do well with cabbage, cranberry, cilantro, and collard greens — with the usual caveat that any single yard's soil, sun, and drainage cast the deciding vote.
Grounded in USDA PHZM 2023 · Growable Ground suitability scoring · NOAA 1991–2020 Climate Normals
Mountrail County holds more than one microclimate.
Soils and elevations shift across Mountrail 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 Mountrail County — soil, climate, flood, and parcel records. How we handle your address.
No card required · your full report in seconds
Mountrail County — the short answer
Mountrail County, North Dakota: USDA zone 4a, about 147 days between hard freezes, across 1.2M acres.
- USDA zone
- 4a
- USDA PHZM 2023
- Last hard freeze (28°F)
- May 6
- NOAA 1991–2020 Climate Normals, 28°F
- First hard freeze (28°F)
- Sep 30
- NOAA 1991–2020 Climate Normals, 28°F
- Days between freezes
- ~147
- NOAA 1991–2020 Climate Normals, 28°F
- County area
- 1.2M 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 4a is Mountrail County's average, not your lot's — a low corner or a tree line moves it. Against Mountrail County's 147-day season, see what your own ground reads.
Heat in Mountrail County
Across a year, Mountrail County accumulates about 1,572 growing degree days above 50°F, about 341 fewer than the middle North Dakota county — ahead of 2 of North Dakota’s 53 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 Mountrail County
Across Mountrail County, the ground is predominantly Mollisols, where Williams, Zahl, and Bowbells are the most extensive named soil series. The soil is generally well drained with a loam surface. Topsoil pH runs about 7.0–7.9, slightly alkaline. Rainfall drains through hydrologic group B soils.
Soil order
Mollisols
Drainage
Well drained
Prime farmland
2%
Hydric soils
9%
Soil still varies lot by lot — soil types explained.
How the ground varies across Mountrail County
The USDA soil survey maps 75% of Mountrail County as well drained — but another 19% drains differently: 4% very poorly drained, 4% excessively drained.
Williams is the most extensive named soil at 32% of mapped acres, then Zahl (24%) and Bowbells (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 Mountrail County
Each reading below is measured for Mountrail 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 Mountrail County are well drained, in hydrologic group B — 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 Mountrail County runs about pH 7.0–7.9, 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
MeasuredMountrail County runs about 147 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
MeasuredMountrail 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 Mountrail County is in
Mountrail County spans 2 EPA Level III ecoregions — Northwestern Glaciated Plains (81%) and Northwestern Great Plains (18%). 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 Mountrail County
We scored all 1,086 plants against Mountrail County's own USDA zone 4a and its own 147-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 North Dakota profile.
Is it too late to plant in Mountrail 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 8; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near May 6 (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 Mountrail County
USGS estimates 338,663 lb of Glyphosate on Mountrail County farmland in 2019, its largest by weight, ahead of 2,4-d (29,084 lb) and Bromoxynil (28,977 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 Mountrail County — and how to grow with it.
We checked the federal record across Mountrail County — 425 documented sites across 4 of the 9 source types we track.
The most significant on record: 9 Toxics Release Inventory facilities. Active industrial facilities reporting chemical releases to air, water, and land.
There's a meaningful federal record across Mountrail 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 Mountrail County
Closest first, across Mountrail County. Listing isn't leaking, and distance isn't exposure.
- Minot Air Force BaseUnderground Storage Tanks · 2400 ft
- Belden StoreUnderground Storage Tanks · 2.5 mi
- ANDEAVOR FIELD SERVICES LLC - STANLEY COMPRESSOR STATIONToxics Release Inventory · 3.1 mi
- STANLEY BOOSTER STATIONBrownfields · 3.1 mi
- 154-090-06CCANitrate · 3.2 mi
- 154-091-15CDC2Nitrate · 3.8 mi
- 155-091-07CDCNitrate · 4.4 mi
- 154-090-18CDDNitrate · 4.8 mi
- 154-091-30AAANitrate · 5.6 mi
- 156-091-33ACCNitrate · 5.7 mi
- PAT'S OFFROAD DBA OIL WORXBrownfields · 6.1 mi
- NORTH AMERICAN TRAILER SALES, LTDBrownfields · 6.1 mi
6 more sites are on the record inside the same radius. See them on the map
Measured from Mountrail 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 Mountrail County.
Total Sites
425
across Mountrail County
Risk Level
Elevated
Highest-severity
9 Toxics Release Inventory facilities
Sources Checked
across Mountrail County
Severity Distribution
across Mountrail County
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around Mountrail County, Nitrate runs higher than the national average — 312 sites across Mountrail 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 Mountrail 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 Mountrail County average
Your land is one point inside Mountrail County
Everything above resolves to Mountrail County as a whole — one PHZM band and one county frost record, read across 1.2M 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 Mountrail County Average
Mountrail County Average
- ●USDA Zones 4a, averaged across Mountrail County
- ●One soil character for all of Mountrail County
- ●Frost dates read at Mountrail County's scale: May 6 to Sep 30
YOUR Parcel
- ✓Your exact zone, not Mountrail County's 4a
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your parcel in Mountrail County
Pull a site-specific report for your exact address in Mountrail County, North Dakota — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Mountrail County averages can't show:
We read public map data around Mountrail County — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Mountrail County average
How we know this about Mountrail 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 Mountrail County carries no record of its own, the figure is inherited and labelled — the resolution ledger below names each.
Common questions about Mountrail County
When does frost risk typically end in Mountrail County?
The last hard freeze (28°F) in Mountrail County typically lands around May 6, 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 27.
How long is the growing season in Mountrail County?
Measured between 28°F hard freezes, Mountrail County sees about 147 frost-free days — roughly May 6 through Sep 30, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer May 27 to Sep 16, about 112 days.
Is the soil safe to grow vegetables in Mountrail County?
The federal record around Mountrail County is a meaningful one — 425 documented sites, mostly Nitrate entries (312), the nearest Underground Storage Tanks record about 0.5 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 Mountrail County?
With about 147 frost-free days between hard freezes, Mountrail 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 175 to 203 days — and cold frames or low tunnels buy more. Starting transplants indoors ahead of the May 6 hard-freeze normal stretches the season without touching the calendar.
Everything above is measured at Mountrail County's scale — its 4a band and its 147-day season. Your yard writes its own version of Mountrail 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 North Dakota's frost window, season length, and soil profile against the plant's real requirements.
What this page reads at Mountrail County’s own scale
8 of the readings below were taken at Mountrail County's own scale — its own ~147-day span between 28°F freezes, the 3 most extensive soil series mapped here and 425 documented sites inside its boundary; one is borrowed from a wider read, named and linked below.
Measured here
- Mountrail County's own USDA hardiness band, zones 4aUSDA PHZM 2023
- Mountrail County's own 28°F hard-freeze dates and its ~147-day span between themNOAA 1991–2020 Climate Normals
- The soil order, drainage, surface pH, and the 3 most extensive named soil series mapped in Mountrail CountyUSDA NRCS SSURGO
- 425 documented contamination sites inside the county boundary, distance-sorted from its center — the closest Underground Storage Tanks record about 0.5 miles outFederal environmental registers
- Mountrail County's boundary and the 1,168,103 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 4a and a ~147-day seasonGrowable Ground crop-matching engine
- The 2 ecoregions Mountrail County spans, Northwestern Glaciated Plains the largestUS EPA Level III Ecoregions
- Which agricultural compounds go onto Mountrail County farmland, and roughly how muchUSGS NAWQA EPest county estimates
Inherited from a wider read
- The growing challenges every North Dakota grower plans around — written at state scale, so they stay on the state guidefrom North Dakota
What this page can’t tell you
- How the season shifts across Mountrail County — the ~147 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 Mountrail County's 1,168,103 acreswhy one lot differs from the next →
- Which of those 425 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 Mountrail Countyread your own land →