Corwin Springs, Montana, sits in USDA hardiness zone 5a — room for a real mix of vegetables, fruit, and perennials matched to the local frost calendar.
Expect cabbage, cranberry, lavender, and collard greens to be strong candidates here; the deciding factors on any one parcel stay local — soil, sun, and drainage.
Even in Corwin Springs, 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 Corwin Springs 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 Corwin Springs — soil, climate, flood, and parcel records. How we handle your address.
No card required · your full report in seconds
Corwin Springs — the short answer
Corwin Springs, Montana: USDA zone 5a, about 144 days between hard freezes, across 901 acres of town.
- USDA zone
- 5a
- USDA PHZM 2023
- Last hard freeze (28°F)
- May 12
- NOAA 1991–2020 Climate Normals, 28°F — this town
- First hard freeze (28°F)
- Oct 3
- NOAA 1991–2020 Climate Normals, 28°F — this town
- Days between freezes
- ~144
- NOAA 1991–2020 Climate Normals, 28°F — this town
- Town area
- 901 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 5a is Corwin Springs's average, not your lot's — a low corner or a tree line moves it. Against Corwin Springs's 144-day season, see what your own ground reads.
Soil varies lot by lot — soil types explained.
What this means for growing in Corwin Springs
Each reading below is measured for Corwin Springs itself — here is what it means for a garden here, and the move an experienced grower makes about it.
Season length
MeasuredCorwin Springs runs about 144 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
MeasuredCorwin Springs sits in USDA hardiness zone 5a.
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 Corwin Springs is in
Corwin Springs sits in the Middle Rockies — EPA Level III, inside the wider Northwestern Forested Mountains. That is read at Corwin Springs's own centroid rather than borrowed from Park County.
What Grows in Corwin Springs
Every plant below cleared Corwin Springs's own zone 5a and its 144-day season. Each card opens that plant's Montana profile. How we score.
Is it too late to plant in Corwin Springs?
Almost never — the real question is what to plant next. Cool-season crops can go in from around Apr 14; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near May 12 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Oct 3 — long-season crops need about 90 days of runway, quick greens only 30. In a season this compact, fast finishers and cold-hardy greens do the late work, and garlic tucked in before the freeze repays you next summer.
What's on the federal record near Corwin Springs
Closest first, within ~10 miles of Corwin Springs. Listing isn't leaking, and distance isn't exposure.
- WELCH E BROGANUnderground Storage Tanks · 1.4 mi
- OLD BN DEPOTUnderground Storage Tanks · 2.6 mi
- MDOT CARBELLA SITEUnderground Storage Tanks · 2.6 mi
- GARDINER AIRPORT 3403891Underground Storage Tanks · 2.6 mi
- GARDINER SERVICE CENTERUnderground Storage Tanks · 2.6 mi
- MOL HERON CONFERENCE SITEUnderground Storage Tanks · 3.7 mi
- RANCH OFFICEUnderground Storage Tanks · 4.1 mi
- LIFESAVERS INCUnderground Storage Tanks · 7.1 mi
- CHALLIS WELL SHELTERUnderground Storage Tanks · 7.1 mi
- CAPSTONE SHELTERUnderground Storage Tanks · 7.1 mi
- MARKS ARK INCUnderground Storage Tanks · 7.1 mi
- B BUNK INCUnderground Storage Tanks · 7.1 mi
6 more sites are on the record inside the same radius. See them on the map
Measured from Corwin Springs'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 Corwin Springs.
Sources Checked
within ~10 miles of Corwin Springs
Severity Distribution
within ~10 miles of Corwin Springs
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around Corwin Springs, two things run higher than the national average within ~10 miles of Corwin Springs — Mining (11 sites) and Underground Storage Tanks (25 sites). 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.
Underground Storage Tanks: Underground storage tanks are the single most common source of soil contamination near homes and gardens.
Test soil for heavy metals (lead, arsenic, cadmium, mercury) — this is essential near any mining site.
Use raised beds with imported soil — this eliminates the primary soil-contact pathway.
Check your specific parcel in Corwin Springs
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 Corwin Springs average
Your land is one point inside Corwin Springs
Everything above resolves to Corwin Springs as a whole — one PHZM band and one 28°F frost record, read across 901 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 Corwin Springs Average
Corwin Springs Average
- ●USDA Zones 5a, averaged across Corwin Springs
- ●One soil character for all of Corwin Springs
- ●Frost dates read at Corwin Springs's scale: May 12 to Oct 3
YOUR Parcel
- ✓Your exact zone, not Corwin Springs's 5a
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your specific parcel in Corwin Springs
Pull a site-specific report for your exact address in Corwin Springs, Montana — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Corwin Springs averages can't show:
We read public map data around Corwin Springs — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Corwin Springs average
How we know this about Corwin Springs
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 Corwin Springs’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 Corwin Springs
When does frost risk typically end in Corwin Springs?
The last hard freeze (28°F) in Corwin Springs typically lands around May 12, 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 2.
When is the first frost in Corwin Springs?
The first hard freeze (28°F) in Corwin Springs typically arrives around Oct 3, per NOAA 1991–2020 climate normals — the point tender summer crops finish. Lighter frosts run ahead of it, near Sep 19, so the watching starts about Sep 3 — about 144 days after the spring freeze cleared.
How long is the growing season in Corwin Springs?
Measured between 28°F hard freezes, Corwin Springs sees about 144 frost-free days — roughly May 12 through Oct 3, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer Jun 2 to Sep 19, about 109 days.
Is the soil safe to grow vegetables in Corwin Springs?
The federal record around Corwin Springs is a meaningful one — 37 documented sites, mostly Underground Storage Tanks entries (25), the nearest Underground Storage Tanks record about 1.4 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 Corwin Springs?
With about 144 frost-free days between hard freezes, Corwin Springs 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 172 to 200 days — and cold frames or low tunnels buy more. Starting transplants indoors ahead of the May 12 hard-freeze normal stretches the season without touching the calendar.
Everything above is measured at Corwin Springs's scale — its 5a band and its 144-day season. Your yard writes its own version of Corwin Springs'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 Corwin Springs’s own scale
6 of the readings below were taken at Corwin Springs's own scale — its own ~144-day season between 28°F freezes, the 901 acres it covers and 37 documented sites around it; 4 are borrowed from a wider read, named and linked below.
Measured here
- Corwin Springs's own USDA hardiness band, zones 5aUSDA PHZM 2023
- Corwin Springs's own 28°F hard-freeze dates, about May 12 and Oct 3 and the ~144-day span between themNOAA 1991–2020 Climate Normals
- 37 documented contamination sites on the federal record near Corwin Springs, the closest Underground Storage Tanks record about 1.4 miles out from the town centreFederal environmental registers
- Corwin Springs's boundary and the 901 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 5a and a ~144-day seasonGrowable Ground crop-matching engine
- The ecoregion at Corwin Springs's own centroid, the Middle RockiesUS EPA Level III Ecoregions
Inherited from a wider read
- Soil character — no town-scale survey exists, so Corwin Springs's 901 acres read through its county's SSURGO summaryfrom Park County
- Growing-degree days and winter chill — measured county-wide only, so the county page carries themfrom Park 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 Park County
What this page can’t tell you
- The soil pH, drainage, sun hours, and frost pockets on any one lot among Corwin Springs's 901 acreswhy one lot differs from the next →
- Which side of Corwin Springs you're on — a low spot frosts first and a south wall warms early, and one normal is being asked to speak for all 901 acresreading your own microclimate →
- How close that record sits to YOUR lot — the closest Underground Storage Tanks record about 1.4 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 Corwin Springs-wide figureread your own land →
More in Montana
Growing region
Nearby growing guides