Three Forks, Montana, sits in USDA hardiness zone 4b — a range where zone-matched perennials and frost-aware annual timing set what succeeds.
The conditions favor cabbage, cranberry, turkish rocket, and collard greens, among others — though every individual site edits that list with its own soil, sun, and drainage.
Even in Three Forks, no two yards are alike.
A low spot, a south-facing slope, or a stand of trees moves the frost date and sun across a single Three Forks lot. 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 Three Forks — soil, climate, flood, and parcel records. How we handle your address.
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Three Forks — the short answer
Three Forks, Montana: USDA zone 4b, about 152 days between hard freezes, across 921 acres of city.
- USDA zone
- 4b
- USDA PHZM 2023
- Last hard freeze (28°F)
- May 5
- NOAA 1991–2020 Climate Normals, 28°F — this town
- First hard freeze (28°F)
- Oct 4
- NOAA 1991–2020 Climate Normals, 28°F — this town
- Days between freezes
- ~152
- NOAA 1991–2020 Climate Normals, 28°F — this town
- City area
- 921 acres
- US Census TIGER/Line 2025
Every figure names the dataset it came from. Hard-freeze dates are this town’s own 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 Three Forks's average, not your lot's — a low corner or a tree line moves it. Against Three Forks's 152-day season, see what your own ground reads.
Soil varies lot by lot — soil types explained.
What this means for growing in Three Forks
Each reading below is measured for Three Forks itself — here is what it means for a garden here, and the move an experienced grower makes about it.
Season length
MeasuredThree Forks runs about 152 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
MeasuredThree Forks 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 Three Forks is in
Three Forks sits in the Middle Rockies — EPA Level III, inside the wider Northwestern Forested Mountains. That is read at Three Forks's own centroid rather than borrowed from Gallatin County.
What Grows in Three Forks
Every plant below cleared Three Forks's own zone 4b and its 152-day season. Each card opens that plant's Montana profile. How we score.
Is it too late to plant in Three Forks?
Almost never — the real question is what to plant next. 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 4 — 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.
What's on the federal record near Three Forks
Closest first, within ~10 miles of Three Forks. Listing isn't leaking, and distance isn't exposure.
- CITY OF THREE FORKS USTUnderground Storage Tanks · 550 ft
- THREE FORKS MOTOR SUPPLY INCUnderground Storage Tanks · 1200 ft
- ROB NORMANUnderground Storage Tanks · 1300 ft
- AT & T COMMUNICATIONS THREE FORKS RADIOUnderground Storage Tanks · 1400 ft
- RALPH GREENUnderground Storage Tanks · 1400 ft
- FORMER MWRR THREE FORKSUnderground Storage Tanks · 1400 ft
- GALLATIN FLYING CLUBUnderground Storage Tanks · 1400 ft
- THREE FORKS FLYING CLUBUnderground Storage Tanks · 1400 ft
- BN THREE FORKS MICROWAVEUnderground Storage Tanks · 1400 ft
- THREE FORKS TALC MILLUnderground Storage Tanks · 1400 ft
- BN LOMBARD MICROWAVE SITEUnderground Storage Tanks · 1400 ft
- KANTA PRODUCTS INC USTUnderground Storage Tanks · 1400 ft
6 more sites are on the record inside the same radius. See them on the map
Measured from Three Forks'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 Three Forks.
Total Sites
188
within ~10 miles of Three Forks
Risk Level
Moderate
Highest-severity
1 Toxics Release Inventory facility
Sources Checked
within ~10 miles of Three Forks
Severity Distribution
within ~10 miles of Three Forks
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around Three Forks, two things run higher than the national average within ~10 miles of Three Forks — Nitrate (138 sites) and CAFO (3 sites). 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.
CAFO: CAFOs pose a different contamination profile than chemical sources.
Test well water for nitrate if you rely on a private well for irrigation (EPA standard: 10 mg/L).
Wash all produce consumed raw thoroughly, especially leafy greens grown near CAFOs.
Check your specific parcel in Three Forks
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 Three Forks average
Your land is one point inside Three Forks
Everything above resolves to Three Forks as a whole — one PHZM band and one 28°F frost record, read across 921 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 city 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 local average.
Your Lot vs the Three Forks Average
Three Forks Average
- ●USDA Zones 4b, averaged across Three Forks
- ●One soil character for all of Three Forks
- ●Frost dates read at Three Forks's scale: May 5 to Oct 4
YOUR Parcel
- ✓Your exact zone, not Three Forks's 4b
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your specific parcel in Three Forks
Pull a site-specific report for your exact address in Three Forks, Montana — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Three Forks averages can't show:
We read public map data around Three Forks — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Three Forks average
How we know this about Three Forks
The datasets: hardiness from the USDA ARS Plant Hardiness Zone Map 2023, read at this city’s own centroid; hard-freeze dates from NOAA 1991–2020 28°F normals at Three Forks’s own record; boundaries and acreage from US Census TIGER/Line 2025; the contamination records from the federal sources named in their beats above. Soil is not read at city grain anywhere on this page — there is no city-resolution survey in our data, which is why you will find no soil grid here rather than a statewide one wearing a local label. The resolution ledger below names every figure this page inherited.
Common questions about Three Forks
When does frost risk typically end in Three Forks?
The last hard freeze (28°F) in Three Forks 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.
When is the first frost in Three Forks?
The first hard freeze (28°F) in Three Forks typically arrives around Oct 4, per NOAA 1991–2020 climate normals — the point tender summer crops finish. Lighter frosts run ahead of it, near Sep 20, so the watching starts about Sep 4 — about 152 days after the spring freeze cleared.
How long is the growing season in Three Forks?
Measured between 28°F hard freezes, Three Forks sees about 152 frost-free days — roughly May 5 through Oct 4, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer May 26 to Sep 20, about 117 days.
Is the soil safe to grow vegetables in Three Forks?
The federal record around Three Forks shows 188 documented sites, mostly Nitrate entries (138), the nearest Underground Storage Tanks record about 0.1 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.
How do I protect my plants from frost in Three Forks?
From about Sep 4 the job here turns from planting to protecting — the last start even a 30-day crop can finish. As the season closes around the first 28°F hard freeze near Oct 4 (NOAA 1991–2020 climate normals), three moves buy time: row cover or an old sheet over tender plants on still, clear nights; water the soil the afternoon before a freeze, so it holds warmth overnight; and harvest tomatoes, peppers and basil before Oct 4. Hardy greens and roots shrug off light frost and sweeten after it — leave them in.
Everything above is measured at Three Forks's scale — its 4b band and its 152-day season. Your yard writes its own version of Three Forks's numbers: we read soil, sun, drainage and frost at your exact address. Try it for 14 days — no card required.
What this page reads at Three Forks’s own scale
6 of the readings below were taken at Three Forks's own scale — its own ~152-day season between 28°F freezes, the 921 acres it covers and 188 documented sites around it; 4 are borrowed from a wider read, named and linked below.
Measured here
- Three Forks's own USDA hardiness band, zones 4bUSDA PHZM 2023
- Three Forks's own 28°F hard-freeze dates, about May 5 and Oct 4 and the ~152-day span between themNOAA 1991–2020 Climate Normals
- 188 documented contamination sites on the federal record near Three Forks, the closest Underground Storage Tanks record about 0.1 miles out from the town centreFederal environmental registers
- Three Forks's boundary and the 921 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 4b and a ~152-day seasonGrowable Ground crop-matching engine
- The ecoregion at Three Forks's own centroid, the Middle RockiesUS EPA Level III Ecoregions
Inherited from a wider read
- Soil character — no town-scale survey exists, so Three Forks's 921 acres read through its county's SSURGO summaryfrom Gallatin County
- Growing-degree days and winter chill — measured county-wide only, so the county page carries themfrom Gallatin County
- The growing challenges every Montana grower plans around — written at state scale, so they stay on the state guidefrom Montana
- Butterfly and beetle records, and the farmland pesticide estimate — all published county-widefrom Gallatin County
What this page can’t tell you
- The soil pH, drainage, sun hours, and frost pockets on any one lot among Three Forks's 921 acreswhy one lot differs from the next →
- Which side of Three Forks you're on — a low spot frosts first and a south wall warms early, and one normal is being asked to speak for all 921 acresreading your own microclimate →
- How close that record sits to YOUR lot — the closest Underground Storage Tanks record about 0.1 miles out, measured from the town centrehow we read the record →
- Where cold air settles, which slopes face the sun, and which way the wind runs on your own ground — measured at your address, and averaged away by any Three Forks-wide figureread your own land →
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