Mills, Wyoming, sits in USDA hardiness zone 5a — a band that supports both cool-season staples and warm-season crops chosen to fit the local frost window.
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 Mills, 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 Mills 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 Mills — soil, climate, flood, and parcel records. How we handle your address.
No card required · your full report in seconds
Mills — the short answer
Mills, Wyoming: USDA zone 5a, about 155 days between hard freezes, across 3K acres of town.
- USDA zone
- 5a
- USDA PHZM 2023
- Last hard freeze (28°F)
- May 5
- NOAA 1991–2020 Climate Normals, 28°F — this town
- First hard freeze (28°F)
- Oct 7
- NOAA 1991–2020 Climate Normals, 28°F — this town
- Days between freezes
- ~155
- NOAA 1991–2020 Climate Normals, 28°F — this town
- Town area
- 3K 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 Mills's average, not your lot's — a low corner or a tree line moves it. Against Mills's 155-day season, see what your own ground reads.
Soil varies lot by lot — soil types explained.
What this means for growing in Mills
Each reading below is measured for Mills itself — here is what it means for a garden here, and the move an experienced grower makes about it.
Season length
MeasuredMills runs about 155 days between hard freezes — a moderate growing season.
There is room for the full run of cool-season crops plus a warm-season main crop, but the calendar is tight enough that a late spring or early fall frost still decides how much finishes.
Time warm-season transplants to your last hard freeze, and a few weeks of season extension turns a near-miss harvest into a sure one.
NOAA 1991–2020 Climate Normals
Winter hardiness
MeasuredMills 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 Mills is in
Mills sits in the Northwestern Great Plains — EPA Level III, inside the wider Great Plains. That is read at Mills'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 Mills
Every plant below cleared Mills's own zone 5a and its 155-day season. Each card opens that plant's Wyoming profile. How we score.
Is it too late to plant in Mills?
Too late for some crops, right on time for others — a growing season is a sequence, not a deadline. Cool-season crops can go in from around Apr 7; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near May 5 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Oct 7 — long-season crops need about 90 days of runway, quick greens only 30. Late in the year the fall bench takes over — quick greens, radishes, and garlic that repays you next summer.
What's on the federal record near Mills
Closest first, within ~10 miles of Mills. Listing isn't leaking, and distance isn't exposure.
- Crimm DrillingUnderground Storage Tanks · 200 ft
- HENDRY STATIONBrownfields · 350 ft
- Marvin ColemanUnderground Storage Tanks · 400 ft
- W. R. MillerUnderground Storage Tanks · 1200 ft
- TALLGRASS MIDSTREAM LLC - CASPER GAS PLANT & COMPRESSOR STATIONBrownfields · 1300 ft
- CULVERTS & INDUSTRIAL SUPPLY COToxics Release Inventory · 1300 ft
- DOWELL SCHLUMBERGER INC.Brownfields · 1300 ft
- TUBOSCOPEToxics Release Inventory · 1300 ft
- RICHARDSON TRUCKINGBrownfields · 1300 ft
- WYOMING MACHINERY COMPANYBrownfields · 1300 ft
- TALLGRASS MIDSTREAM LLC - CASPER GAS PLANT & COMPRESSOR STATIONToxics Release Inventory · 1300 ft
- BAKER PETROLITE, CASPER, WYBrownfields · 1300 ft
6 more sites are on the record inside the same radius. See them on the map
Measured from Mills'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 Mills.
Sources Checked
within ~10 miles of Mills
Severity Distribution
within ~10 miles of Mills
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 Mills
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 Mills average
Your land is one point inside Mills
Everything above resolves to Mills as a whole — one PHZM band and one 28°F frost record, read across 3K 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 Mills Average
Mills Average
- ●USDA Zones 5a, averaged across Mills
- ●One soil character for all of Mills
- ●Frost dates read at Mills's scale: May 5 to Oct 7
YOUR Parcel
- ✓Your exact zone, not Mills's 5a
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your specific parcel in Mills
Pull a site-specific report for your exact address in Mills, Wyoming — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Mills averages can't show:
We read public map data around Mills — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Mills average
How we know this about Mills
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 Mills’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 Mills
When does frost risk typically end in Mills?
The last hard freeze (28°F) in Mills typically lands around May 5, 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 26.
When is the first frost in Mills?
The first hard freeze (28°F) in Mills typically arrives around Oct 7, per NOAA 1991–2020 climate normals — the point tender summer crops finish. Lighter frosts run ahead of it, near Sep 23, so the watching starts about Sep 7 — about 155 days after the spring freeze cleared.
How long is the growing season in Mills?
Measured between 28°F hard freezes, Mills sees about 155 frost-free days — roughly May 5 through Oct 7, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer May 26 to Sep 23, about 120 days.
Is the soil safe to grow vegetables in Mills?
The federal record around Mills is a meaningful one — 814 documented sites, mostly Underground Storage Tanks entries (454), the nearest Underground Storage Tanks record under a tenth of a mile 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 I protect my plants from frost in Mills?
From about Sep 7 the job here turns from planting to protecting — the last start even a 30-day crop can finish. As the season closes around the first 28°F hard freeze near Oct 7 (NOAA 1991–2020 climate normals), three moves buy time: row cover or an old sheet over tender plants on still, clear nights; water the soil the afternoon before a freeze, so it holds warmth overnight; and harvest tomatoes, peppers and basil before Oct 7. Hardy greens and roots shrug off light frost and sweeten after it — leave them in.
Everything above is measured at Mills's scale — its 5a band and its 155-day season. Your yard writes its own version of Mills'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 Mills’s own scale
6 of the readings below were taken at Mills's own scale — its own ~155-day season between 28°F freezes, the 3,260 acres it covers and 814 documented sites around it; 4 are borrowed from a wider read, named and linked below.
Measured here
- Mills's own USDA hardiness band, zones 5aUSDA PHZM 2023
- Mills's own 28°F hard-freeze dates, about May 5 and Oct 7 and the ~155-day span between themNOAA 1991–2020 Climate Normals
- 814 documented contamination sites on the federal record near Mills, the closest Underground Storage Tanks record under a tenth of a mile out from the town centreFederal environmental registers
- Mills's boundary and the 3,260 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 5a and a ~155-day seasonGrowable Ground crop-matching engine
- Mills sits in the Northwestern Great Plains — not the ecoregion its county mostly readsUS EPA Level III Ecoregions
Inherited from a wider read
- Soil character — no town-scale survey exists, so Mills's 3,260 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 Mills's 3,260 acreswhy one lot differs from the next →
- Which side of Mills you're on — a low spot frosts first and a south wall warms early, and one normal is being asked to speak for all 3,260 acresreading your own microclimate →
- How close that record sits to YOUR lot — the closest Underground Storage Tanks 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 Mills-wide figureread your own land →
More in Wyoming
Wider growing context
What grows across WyomingMills sits outside our named growing regions, so Wyoming as a whole is its closest context here.
Nearby growing guides