Helena Flats, Montana, sits in USDA hardiness zone 5b — a band that supports both cool-season staples and warm-season crops chosen to fit the local frost window.
These conditions suit cabbage, cranberry, lavender, and collard greens — a starting list any specific site will trim or extend with its own soil, sun, and drainage.
Even in Helena Flats, 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 Helena Flats 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 Helena Flats — soil, climate, flood, and parcel records. How we handle your address.
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Helena Flats — the short answer
Helena Flats, Montana: USDA zone 5b, about 148 days between hard freezes, across 5K acres of town.
- USDA zone
- 5b
- USDA PHZM 2023
- Last hard freeze (28°F)
- May 6
- NOAA 1991–2020 Climate Normals, 28°F — this town
- First hard freeze (28°F)
- Oct 1
- NOAA 1991–2020 Climate Normals, 28°F — this town
- Days between freezes
- ~148
- NOAA 1991–2020 Climate Normals, 28°F — this town
- Town area
- 5K 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 5b is Helena Flats's average, not your lot's — a low corner or a tree line moves it. Against Helena Flats's 148-day season, see what your own ground reads.
Soil varies lot by lot — soil types explained.
What this means for growing in Helena Flats
Each reading below is measured for Helena Flats itself — here is what it means for a garden here, and the move an experienced grower makes about it.
Season length
MeasuredHelena Flats runs about 148 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
MeasuredHelena Flats sits in USDA hardiness zone 5b.
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 Helena Flats is in
Helena Flats sits in the Northern Rockies — EPA Level III, inside the wider Northwestern Forested Mountains. That is read at Helena Flats's own centroid, and it is not what its county reads: Flathead County is mostly Canadian Rockies. The wider page above you is answering a different question about different ground.
What Grows in Helena Flats
Every plant below cleared Helena Flats's own zone 5b and its 148-day season. Each card opens that plant's Montana profile. How we score.
Is it too late to plant in Helena Flats?
Almost never — the real question is what to plant next. 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 Oct 1 — 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 Helena Flats
Closest first, within ~10 miles of Helena Flats. Listing isn't leaking, and distance isn't exposure.
- 29N21W15CB 01Nitrate · 0.5 mi
- 29N21W11DBDD01Nitrate · 0.7 mi
- MCMANUS TRANSPORTBrownfields · 0.9 mi
- 29N21W22ABBB01Nitrate · 1.1 mi
- ROCCOS STOREUnderground Storage Tanks · 1.2 mi
- APPLIED MATERIALS, PPC BUSINESS UNITBrownfields · 1.3 mi
- KNIFE RIVER - 777-2699Toxics Release Inventory · 1.4 mi
- CITY SERVICE VALCON - EAGLE FUELUnderground Storage Tanks · 1.6 mi
- 29N20W18AA 02Nitrate · 1.7 mi
- BUDGET RENT A CARUnderground Storage Tanks · 1.8 mi
- GLACIER JET CENTERUnderground Storage Tanks · 1.8 mi
- GLACIER PARK INTERNATIONAL AIRPORTUnderground Storage Tanks · 1.8 mi
6 more sites are on the record inside the same radius. See them on the map
Measured from Helena Flats'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 Helena Flats.
Sources Checked
within ~10 miles of Helena Flats
Severity Distribution
within ~10 miles of Helena Flats
Highest-Severity Sites
Know Before You Grow
- •Underground tanks leak petroleum as they age — near a former filling station, test the soil.
- •On a private well, test for nitrates: above 10 mg/L the water needs treatment before irrigating.
- •Near a brownfield, raised beds of imported soil give your food clean ground.
Check your specific parcel in Helena Flats
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 Helena Flats average
Your land is one point inside Helena Flats
Everything above resolves to Helena Flats as a whole — one PHZM band and one 28°F frost record, read across 5K 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 Helena Flats Average
Helena Flats Average
- ●USDA Zones 5b, averaged across Helena Flats
- ●One soil character for all of Helena Flats
- ●Frost dates read at Helena Flats's scale: May 6 to Oct 1
YOUR Parcel
- ✓Your exact zone, not Helena Flats's 5b
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your specific parcel in Helena Flats
Pull a site-specific report for your exact address in Helena Flats, Montana — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Helena Flats averages can't show:
We read public map data around Helena Flats — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Helena Flats average
How we know this about Helena Flats
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 Helena Flats’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 Helena Flats
When does frost risk typically end in Helena Flats?
The last hard freeze (28°F) in Helena Flats 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.
When is the first frost in Helena Flats?
The first hard freeze (28°F) in Helena Flats typically arrives around Oct 1, per NOAA 1991–2020 climate normals — the point tender summer crops finish. Lighter frosts run ahead of it, near Sep 17, so the watching starts about Sep 1 — about 148 days after the spring freeze cleared.
How long is the growing season in Helena Flats?
Measured between 28°F hard freezes, Helena Flats sees about 148 frost-free days — roughly May 6 through Oct 1, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer May 27 to Sep 17, about 113 days.
Is the soil safe to grow vegetables in Helena Flats?
The federal record around Helena Flats is a meaningful one — 420 documented sites, mostly Underground Storage Tanks entries (212), the nearest Nitrate 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 Helena Flats?
With about 148 frost-free days between hard freezes, Helena Flats 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 176 to 204 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 Helena Flats's scale — its 5b band and its 148-day season. Your yard writes its own version of Helena Flats'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 Helena Flats’s own scale
6 of the readings below were taken at Helena Flats's own scale — its own ~148-day season between 28°F freezes, the 5,397 acres it covers and 420 documented sites around it; 4 are borrowed from a wider read, named and linked below.
Measured here
- Helena Flats's own USDA hardiness band, zones 5bUSDA PHZM 2023
- Helena Flats's own 28°F hard-freeze dates, about May 6 and Oct 1 and the ~148-day span between themNOAA 1991–2020 Climate Normals
- 420 documented contamination sites on the federal record near Helena Flats, the closest Nitrate record about 0.5 miles out from the town centreFederal environmental registers
- Helena Flats's boundary and the 5,397 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 5b and a ~148-day seasonGrowable Ground crop-matching engine
- Helena Flats sits in the Northern Rockies — not the ecoregion its county mostly readsUS EPA Level III Ecoregions
Inherited from a wider read
- Soil character — no town-scale survey exists, so Helena Flats's 5,397 acres read through its county's SSURGO summaryfrom Flathead County
- Growing-degree days and winter chill — measured county-wide only, so the county page carries themfrom Flathead 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 Flathead County
What this page can’t tell you
- The soil pH, drainage, sun hours, and frost pockets on any one lot among Helena Flats's 5,397 acreswhy one lot differs from the next →
- Which side of Helena Flats you're on — a low spot frosts first and a south wall warms early, and one normal is being asked to speak for all 5,397 acresreading your own microclimate →
- How close that record sits to YOUR lot — the closest Nitrate 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 Helena Flats-wide figureread your own land →
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