Casper Mountain, Wyoming, sits in USDA hardiness zone 5a — enough range to grow cool-season vegetables, hardy fruit, and warm-season crops that mature before the first hard frost.
Among the crops suited to this profile: cabbage, cranberry, lavender, and collard greens. The site-level story — soil, sun, drainage — decides the rest.
Even in Casper Mountain, 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 Casper Mountain 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 Casper Mountain — soil, climate, flood, and parcel records. How we handle your address.
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Casper Mountain — the short answer
Casper Mountain, Wyoming: USDA zone 5a, about 136 days between hard freezes, across 23K acres of town.
- USDA zone
- 5a
- USDA PHZM 2023
- Last hard freeze (28°F)
- May 17
- NOAA 1991–2020 Climate Normals, 28°F — this town
- First hard freeze (28°F)
- Sep 30
- NOAA 1991–2020 Climate Normals, 28°F — this town
- Days between freezes
- ~136
- NOAA 1991–2020 Climate Normals, 28°F — this town
- Town area
- 23K 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 Casper Mountain's average, not your lot's — a low corner or a tree line moves it. Against Casper Mountain's 136-day season, see what your own ground reads.
Soil varies lot by lot — soil types explained.
What this means for growing in Casper Mountain
Each reading below is measured for Casper Mountain itself — here is what it means for a garden here, and the move an experienced grower makes about it.
Season length
MeasuredCasper Mountain runs about 136 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
MeasuredCasper Mountain 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 Casper Mountain is in
Casper Mountain sits in the Southern Rockies — EPA Level III, inside the wider Northwestern Forested Mountains. That is read at Casper Mountain's own centroid, and it is not what its county reads: Natrona County is mostly Wyoming Basin. The wider page above you is answering a different question about different ground.
What Grows in Casper Mountain
Every plant below cleared Casper Mountain's own zone 5a and its 136-day season. Each card opens that plant's Wyoming profile. How we score.
Is it too late to plant in Casper Mountain?
Almost never — the real question is what to plant next. Cool-season crops can go in from around Apr 19; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near May 17 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Sep 30 — 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 Casper Mountain
Closest first, within ~10 miles of Casper Mountain. Listing isn't leaking, and distance isn't exposure.
- Casper Mountain MineMining · 0.9 mi
- Bucknum SidingUnderground Storage Tanks · 1.4 mi
- ROCKY MTN BRAKE & SUPPLYBrownfields · 1.4 mi
- City of Casper - Hogadon Ski FacilityUnderground Storage Tanks · 1.5 mi
- Natrona County - Casper Mountain Service BuildingUnderground Storage Tanks · 1.8 mi
- Don H. GallesUnderground Storage Tanks · 3.9 mi
- Loaf 'N Jug #106Underground Storage Tanks · 4.9 mi
- AMOCO OIL SS# 8581Brownfields · 5.1 mi
- Sunrise Conoco 8581Underground Storage Tanks · 5.1 mi
- William C. WilfongUnderground Storage Tanks · 5.6 mi
- 33-079-24acc01Nitrate · 5.6 mi
- CUSTOM FIBERGLASS INCToxics Release Inventory · 5.8 mi
6 more sites are on the record inside the same radius. See them on the map
Measured from Casper Mountain'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 Casper Mountain.
Total Sites
677
within ~10 miles of Casper Mountain
Risk Level
Elevated
Highest-severity
3 Superfund sites
Sources Checked
within ~10 miles of Casper Mountain
Severity Distribution
within ~10 miles of Casper Mountain
Highest-Severity Sites
Know Before You Grow
- •Underground tanks leak petroleum as they age — near a former filling station, test the soil.
- •Near a brownfield, raised beds of imported soil give your food clean ground.
- •TRI facilities report what they release. Check the wind — downwind beds catch more of it.
Check your specific parcel in Casper Mountain
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 Casper Mountain average
Your land is one point inside Casper Mountain
Everything above resolves to Casper Mountain as a whole — one PHZM band and one 28°F frost record, read across 23K 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 Casper Mountain Average
Casper Mountain Average
- ●USDA Zones 5a, averaged across Casper Mountain
- ●One soil character for all of Casper Mountain
- ●Frost dates read at Casper Mountain's scale: May 17 to Sep 30
YOUR Parcel
- ✓Your exact zone, not Casper Mountain's 5a
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your specific parcel in Casper Mountain
Pull a site-specific report for your exact address in Casper Mountain, Wyoming — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Casper Mountain averages can't show:
We read public map data around Casper Mountain — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Casper Mountain average
How we know this about Casper Mountain
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 Casper Mountain’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 Casper Mountain
When does frost risk typically end in Casper Mountain?
The last hard freeze (28°F) in Casper Mountain typically lands around May 17, 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 7.
When is the first frost in Casper Mountain?
The first hard freeze (28°F) in Casper Mountain typically arrives around Sep 30, per NOAA 1991–2020 climate normals — the point tender summer crops finish. Lighter frosts run ahead of it, near Sep 16, so the watching starts about Aug 31 — about 136 days after the spring freeze cleared.
How long is the growing season in Casper Mountain?
Measured between 28°F hard freezes, Casper Mountain sees about 136 frost-free days — roughly May 17 through Sep 30, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer Jun 7 to Sep 16, about 101 days.
Is the soil safe to grow vegetables in Casper Mountain?
The federal record around Casper Mountain is a meaningful one — 677 documented sites, mostly Underground Storage Tanks entries (398), the nearest Mining record about 0.9 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 Casper Mountain?
With about 136 frost-free days between hard freezes, Casper Mountain 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 164 to 192 days — and cold frames or low tunnels buy more. Starting transplants indoors ahead of the May 17 hard-freeze normal stretches the season without touching the calendar.
Everything above is measured at Casper Mountain's scale — its 5a band and its 136-day season. Your yard writes its own version of Casper Mountain'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 Casper Mountain’s own scale
6 of the readings below were taken at Casper Mountain's own scale — its own ~136-day season between 28°F freezes, the 22,950 acres it covers and 677 documented sites around it; 4 are borrowed from a wider read, named and linked below.
Measured here
- Casper Mountain's own USDA hardiness band, zones 5aUSDA PHZM 2023
- Casper Mountain's own 28°F hard-freeze dates, about May 17 and Sep 30 and the ~136-day span between themNOAA 1991–2020 Climate Normals
- 677 documented contamination sites on the federal record near Casper Mountain, the closest Mining record about 0.9 miles out from the town centreFederal environmental registers
- Casper Mountain's boundary and the 22,950 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 5a and a ~136-day seasonGrowable Ground crop-matching engine
- Casper Mountain sits in the Southern 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 Casper Mountain's 22,950 acres read through its county's SSURGO summaryfrom Natrona County
- Growing-degree days and winter chill — measured county-wide only, so the county page carries themfrom Natrona County
- The growing challenges every Wyoming grower plans around — written at state scale, so they stay on the state guidefrom Wyoming
- Butterfly and beetle records, and the farmland pesticide estimate — all published county-widefrom Natrona County
What this page can’t tell you
- The soil pH, drainage, sun hours, and frost pockets on any one lot among Casper Mountain's 22,950 acreswhy one lot differs from the next →
- Which side of Casper Mountain you're on — a low spot frosts first and a south wall warms early, and one normal is being asked to speak for all 22,950 acresreading your own microclimate →
- How close that record sits to YOUR lot — the closest Mining record about 0.9 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 Casper Mountain-wide figureread your own land →
More in Wyoming
Wider growing context
What grows across WyomingCasper Mountain sits outside our named growing regions, so Wyoming as a whole is its closest context here.
Nearby growing guides