Windham, Montana, sits in USDA hardiness zone 4b — enough range to grow cool-season vegetables, hardy fruit, and warm-season crops that mature before the first hard frost.
Well-matched crops include cabbage, cranberry, cilantro, and collard greens, and the gap between "grows in the area" and "grows in your yard" is closed by soil, sun, and drainage.
Even in Windham, 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 Windham 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 Windham — soil, climate, flood, and parcel records. How we handle your address.
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Windham — the short answer
Windham, Montana: USDA zone 4b, about 147 days between hard freezes, across 266 acres of town.
- USDA zone
- 4b
- USDA PHZM 2023
- Last hard freeze (28°F)
- May 7
- 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
- ~147
- NOAA 1991–2020 Climate Normals, 28°F — this town
- Town area
- 266 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 Windham's average, not your lot's — a low corner or a tree line moves it. Against Windham's 147-day season, see what your own ground reads.
Soil varies lot by lot — soil types explained.
What this means for growing in Windham
Each reading below is measured for Windham itself — here is what it means for a garden here, and the move an experienced grower makes about it.
Season length
MeasuredWindham 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
MeasuredWindham 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 Windham is in
Windham sits in the Northwestern Great Plains — EPA Level III, inside the wider Great Plains. That is read at Windham's own centroid rather than borrowed from Judith Basin County.
What Grows in Windham
Every plant below cleared Windham's own zone 4b and its 147-day season. Each card opens that plant's Montana profile. How we score.
Is it too late to plant in Windham?
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 Oct 1 — long-season crops need about 90 days of runway, quick greens only 30. Even here the calendar’s edges hold value: thirty-day greens late in the window, then garlic and a rested bed for spring.
What's on the federal record near Windham
Closest first, within ~10 miles of Windham. Listing isn't leaking, and distance isn't exposure.
- 15N12E12ADAC01Nitrate · 250 ft
- SYLVAN WARDUnderground Storage Tanks · 450 ft
- MALMSTROM AFB B 3Underground Storage Tanks · 1100 ft
- 15N12E12AACA01Nitrate · 1200 ft
- 15N12E12DA 01Nitrate · 2000 ft
- August No. 2 Tunnel of Liberty MineMining · 2500 ft
- 15N12E13BABB01Nitrate · 0.9 mi
- 15N12E01CB 01Nitrate · 1.0 mi
- MALMSTROM AFB C 9Underground Storage Tanks · 1.2 mi
- MALMSTROM AFB C 11Underground Storage Tanks · 1.2 mi
- MALMSTROM AFB C 10Underground Storage Tanks · 1.2 mi
- MALMSTROM AFB C 8Underground Storage Tanks · 1.2 mi
6 more sites are on the record inside the same radius. See them on the map
Measured from Windham'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 Windham.
Total Sites
127
within ~10 miles of Windham
Risk Level
Moderate
Highest-severity
1 mining site (prospects, none worked)
Sources Checked
within ~10 miles of Windham
Severity Distribution
within ~10 miles of Windham
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around Windham, Nitrate runs higher than the national average — 92 sites within ~10 miles of Windham. It's not cause for alarm — it's worth knowing, and there's a sensible way to grow around it.
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 Windham
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 Windham average
Your land is one point inside Windham
Everything above resolves to Windham as a whole — one PHZM band and one 28°F frost record, read across 266 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 Windham Average
Windham Average
- ●USDA Zones 4b, averaged across Windham
- ●One soil character for all of Windham
- ●Frost dates read at Windham's scale: May 7 to Oct 1
YOUR Parcel
- ✓Your exact zone, not Windham's 4b
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your specific parcel in Windham
Pull a site-specific report for your exact address in Windham, Montana — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Windham averages can't show:
We read public map data around Windham — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Windham average
How we know this about Windham
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 Windham’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 Windham
When does frost risk typically end in Windham?
The last hard freeze (28°F) in Windham 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.
When is the first frost in Windham?
The first hard freeze (28°F) in Windham 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 147 days after the spring freeze cleared.
How long is the growing season in Windham?
Measured between 28°F hard freezes, Windham sees about 147 frost-free days — roughly May 7 through Oct 1, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer May 28 to Sep 17, about 112 days.
Is the soil safe to grow vegetables in Windham?
The federal record around Windham shows 127 documented sites, mostly Nitrate entries (92), the nearest Nitrate record under a tenth of a mile 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 gardeners stretch the season in Windham?
With about 147 frost-free days between hard freezes, Windham 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 7 hard-freeze normal stretches the season without touching the calendar.
Everything above is measured at Windham's scale — its 4b band and its 147-day season. Your yard writes its own version of Windham'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 Windham’s own scale
6 of the readings below were taken at Windham's own scale — its own ~147-day season between 28°F freezes, the 266 acres it covers and 127 documented sites around it; 4 are borrowed from a wider read, named and linked below.
Measured here
- Windham's own USDA hardiness band, zones 4bUSDA PHZM 2023
- Windham's own 28°F hard-freeze dates, about May 7 and Oct 1 and the ~147-day span between themNOAA 1991–2020 Climate Normals
- 127 documented contamination sites on the federal record near Windham, the closest Nitrate record under a tenth of a mile out from the town centreFederal environmental registers
- Windham's boundary and the 266 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 4b and a ~147-day seasonGrowable Ground crop-matching engine
- The ecoregion at Windham's own centroid, the Northwestern Great PlainsUS EPA Level III Ecoregions
Inherited from a wider read
- Soil character — no town-scale survey exists, so Windham's 266 acres read through its county's SSURGO summaryfrom Judith Basin County
- Growing-degree days and winter chill — measured county-wide only, so the county page carries themfrom Judith Basin 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 Judith Basin County
What this page can’t tell you
- The soil pH, drainage, sun hours, and frost pockets on any one lot among Windham's 266 acreswhy one lot differs from the next →
- Which side of Windham you're on — a low spot frosts first and a south wall warms early, and one normal is being asked to speak for all 266 acresreading your own microclimate →
- How close that record sits to YOUR lot — the closest Nitrate record under a tenth of a mile 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 Windham-wide figureread your own land →
More in Montana
Wider growing context
What grows across MontanaWindham sits outside our named growing regions, so Montana as a whole is its closest context here.
Nearby growing guides