Potomac, Montana, sits in USDA hardiness zone 4b — a band that supports both cool-season staples and warm-season crops chosen to fit the local frost window.
The conditions favor okra, cranberry, cilantro, and zucchini, among others — though every individual site edits that list with its own soil, sun, and drainage.
Even in Potomac, 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 Potomac 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 Potomac — soil, climate, flood, and parcel records. How we handle your address.
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Potomac — the short answer
Potomac, Montana: USDA zone 4b, about 110 days between hard freezes, across 176 acres of town.
- USDA zone
- 4b
- USDA PHZM 2023
- Last hard freeze (28°F)
- May 26
- NOAA 1991–2020 Climate Normals, 28°F — this town
- First hard freeze (28°F)
- Sep 13
- NOAA 1991–2020 Climate Normals, 28°F — this town
- Days between freezes
- ~110
- NOAA 1991–2020 Climate Normals, 28°F — this town
- Town area
- 176 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 Potomac's average, not your lot's — a low corner or a tree line moves it. Against Potomac's 110-day season, see what your own ground reads.
Soil varies lot by lot — soil types explained.
What this means for growing in Potomac
Each reading below is measured for Potomac itself — here is what it means for a garden here, and the move an experienced grower makes about it.
Season length
MeasuredPotomac runs about 110 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
MeasuredPotomac 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 Potomac is in
Potomac sits in the Middle Rockies — EPA Level III, inside the wider Northwestern Forested Mountains. That is read at Potomac's own centroid rather than borrowed from Missoula County.
What Grows in Potomac
Every plant below cleared Potomac's own zone 4b and its 110-day season. Each card opens that plant's Montana profile. How we score.
Is it too late to plant in Potomac?
Rarely: the season closes in stages, not all at once, and each stage has its crops. Cool-season crops can go in from around Apr 28; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near May 26 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Sep 13 — long-season crops need about 90 days of runway, quick greens only 30. Short seasons reward decisiveness — quick-maturing varieties late, hardy greens under cover, and next year’s garlic in the ground before it closes.
What's on the federal record near Potomac
Closest first, within ~10 miles of Potomac. Listing isn't leaking, and distance isn't exposure.
- Copper KingMining · 0.5 mi
- JMBC INCUnderground Storage Tanks · 0.7 mi
- WILDWEST TRADING POSTUnderground Storage Tanks · 1.4 mi
- GREENOUGH HILL CABIN FORMER GAS STATIONUnderground Storage Tanks · 1.4 mi
- ChesterMining · 2.5 mi
- FITZPATRICK TRANSPORTATIONUnderground Storage Tanks · 3.3 mi
- POTOMAC COUNTY STOREUnderground Storage Tanks · 3.3 mi
- CLEARWATER STATE FOREST HDQTSUnderground Storage Tanks · 3.3 mi
- CURRY ROBERT BUnderground Storage Tanks · 3.3 mi
- COMET MINEUnderground Storage Tanks · 3.3 mi
- Mcdonald-Southerland ProspectMining · 4.4 mi
- Adaline MineMining · 4.4 mi
6 more sites are on the record inside the same radius. See them on the map
Measured from Potomac'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 Potomac.
Severity Distribution
within ~10 miles of Potomac
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around Potomac, Mining runs higher than the national average — 71 sites within ~10 miles of Potomac. It's not cause for alarm — it's worth knowing, and there's a sensible way to grow around it.
Mining: Mining sites — both historic and active — can leach heavy metals (arsenic, lead, cadmium, mercury) into soil and water for centuries after operations cease.
Test soil for heavy metals (lead, arsenic, cadmium, mercury) — this is essential near any mining site.
Check your specific parcel in Potomac
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 Potomac average
Your land is one point inside Potomac
Everything above resolves to Potomac as a whole — one PHZM band and one 28°F frost record, read across 176 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 town 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 Potomac Average
Potomac Average
- ●USDA Zones 4b, averaged across Potomac
- ●One soil character for all of Potomac
- ●Frost dates read at Potomac's scale: May 26 to Sep 13
YOUR Parcel
- ✓Your exact zone, not Potomac's 4b
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your specific parcel in Potomac
Pull a site-specific report for your exact address in Potomac, Montana — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Potomac averages can't show:
We read public map data around Potomac — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Potomac average
How we know this about Potomac
The datasets: hardiness from the USDA ARS Plant Hardiness Zone Map 2023, read at this town’s own centroid; hard-freeze dates from NOAA 1991–2020 28°F normals at Potomac’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 town grain anywhere on this page — there is no town-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 Potomac
When does frost risk typically end in Potomac?
The last hard freeze (28°F) in Potomac typically lands around May 26, 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 Jun 16.
When is the first frost in Potomac?
The first hard freeze (28°F) in Potomac typically arrives around Sep 13, per NOAA 1991–2020 climate normals — the point tender summer crops finish. Lighter frosts run ahead of it, near Aug 30, so the watching starts about Aug 14 — about 110 days after the spring freeze cleared.
How long is the growing season in Potomac?
Measured between 28°F hard freezes, Potomac sees about 110 frost-free days — roughly May 26 through Sep 13, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer Jun 16 to Aug 30, about 75 days.
Is the soil safe to grow vegetables in Potomac?
The federal record around Potomac runs heavier than most — 82 documented sites, mostly Mining entries (71), the nearest Mining record about 0.5 miles out — so test the soil before planting food in the ground, and raised beds with clean imported soil grow well in the meantime. Even here, proximity to a documented site is information, not a diagnosis of any one yard; the contamination map shows exactly what's recorded and where.
How do gardeners stretch the season in Potomac?
With about 110 frost-free days between hard freezes, Potomac 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 138 to 166 days — and cold frames or low tunnels buy more. Starting transplants indoors ahead of the May 26 hard-freeze normal stretches the season without touching the calendar.
Everything above is measured at Potomac's scale — its 4b band and its 110-day season. Your yard writes its own version of Potomac'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 Potomac’s own scale
6 of the readings below were taken at Potomac's own scale — its own ~110-day season between 28°F freezes, the 176 acres it covers and 82 documented sites around it; 4 are borrowed from a wider read, named and linked below.
Measured here
- Potomac's own USDA hardiness band, zones 4bUSDA PHZM 2023
- Potomac's own 28°F hard-freeze dates, about May 26 and Sep 13 and the ~110-day span between themNOAA 1991–2020 Climate Normals
- 82 documented contamination sites on the federal record near Potomac, the closest Mining record about 0.5 miles out from the town centreFederal environmental registers
- Potomac's boundary and the 176 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 4b and a ~110-day seasonGrowable Ground crop-matching engine
- The ecoregion at Potomac's own centroid, the Middle RockiesUS EPA Level III Ecoregions
Inherited from a wider read
- Soil character — no town-scale survey exists, so Potomac's 176 acres read through its county's SSURGO summaryfrom Missoula County
- Growing-degree days and winter chill — measured county-wide only, so the county page carries themfrom Missoula 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 Missoula County
What this page can’t tell you
- The soil pH, drainage, sun hours, and frost pockets on any one lot among Potomac's 176 acreswhy one lot differs from the next →
- Which side of Potomac you're on — a low spot frosts first and a south wall warms early, and one normal is being asked to speak for all 176 acresreading your own microclimate →
- How close that record sits to YOUR lot — the closest Mining record about 0.5 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 Potomac-wide figureread your own land →
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