Alta, Utah, sits in USDA hardiness zone 6a — a zone band wide enough that plant choice, not possibility, is the interesting question.
Reliable performers under these conditions include cabbage, blackberry, california poppy, and collard greens; what your own ground favors still comes down to its soil, sun, and drainage.
Even in Alta, 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 Alta 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 Alta — soil, climate, flood, and parcel records. How we handle your address.
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Alta — the short answer
Alta, Utah: USDA zone 6a, about 120 days between hard freezes, across 3K acres of town.
- USDA zone
- 6a
- USDA PHZM 2023
- Last hard freeze (28°F)
- Jun 1
- NOAA 1991–2020 Climate Normals, 28°F — this town
- First hard freeze (28°F)
- Sep 29
- NOAA 1991–2020 Climate Normals, 28°F — this town
- Days between freezes
- ~120
- 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 6a is Alta's average, not your lot's — a low corner or a tree line moves it. Against Alta's 120-day season, see what your own ground reads.
Soil varies lot by lot — soil types explained.
What this means for growing in Alta
Each reading below is measured for Alta itself — here is what it means for a garden here, and the move an experienced grower makes about it.
Season length
MeasuredAlta runs about 120 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
MeasuredAlta sits in USDA hardiness zone 6a.
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 Alta is in
Alta sits in the Wasatch and Uinta Mountains — EPA Level III, inside the wider Northwestern Forested Mountains. That is read at Alta's own centroid, and it is not what its county reads: Salt Lake County is mostly Central Basin and Range. The wider page above you is answering a different question about different ground.
What Grows in Alta
Every plant below cleared Alta's own zone 6a and its 120-day season. Each card opens that plant's Utah profile. How we score.
Is it too late to plant in Alta?
Rarely: the season closes in stages, not all at once, and each stage has its crops. Cool-season crops can go in from around May 4; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near Jun 1 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Sep 29 — 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.
Documented around Alta
Spotted lanternfly documented 17 miles from Alta, first recorded 2020. What to watch for.
What's on the federal record near Alta
Closest first, within ~10 miles of Alta. Listing isn't leaking, and distance isn't exposure.
- Silver StarMining · 850 ft
- IllinoisMining · 850 ft
- Albion TunnelMining · 1600 ft
- Albion MineMining · 1600 ft
- Tillite ClaimsMining · 2100 ft
- VEHICLE MAINTENANCE BLDGUnderground Storage Tanks · 0.7 mi
- Alta-Helena TunnelMining · 0.7 mi
- Emma Silver GroupMining · 0.7 mi
- Little Cottonwood-Big CottonwoodMining · 0.7 mi
- South Hecla MineMining · 0.9 mi
- Michigan Utah MineMining · 0.9 mi
- Buffalo Tunnel MineMining · 0.9 mi
6 more sites are on the record inside the same radius. See them on the map
Measured from Alta'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 Alta.
Sources Checked
within ~10 miles of Alta
Severity Distribution
within ~10 miles of Alta
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around Alta, two things run higher than the national average within ~10 miles of Alta — Mining (474 sites) and Superfund (12 sites). Knowing it is half the work — and it's nothing a thoughtful grower can't plan for.
Mining: Mining sites — both historic and active — can leach heavy metals (arsenic, lead, cadmium, mercury) into soil and water for centuries after operations cease.
Superfund: Superfund sites represent the most severe contamination in the federal system.
Test soil for heavy metals (lead, arsenic, cadmium, mercury) — this is essential near any mining site.
Commission professional soil testing before any food production (test for heavy metals, VOCs, and SVOCs).
Check your specific parcel in Alta
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 Alta average
Your land is one point inside Alta
Everything above resolves to Alta 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 Alta Average
Alta Average
- ●USDA Zones 6a, averaged across Alta
- ●One soil character for all of Alta
- ●Frost dates read at Alta's scale: Jun 1 to Sep 29
YOUR Parcel
- ✓Your exact zone, not Alta's 6a
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your specific parcel in Alta
Pull a site-specific report for your exact address in Alta, Utah — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Alta averages can't show:
We read public map data around Alta — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Alta average
How we know this about Alta
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 Alta’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 Alta
When does frost risk typically end in Alta?
The last hard freeze (28°F) in Alta typically lands around Jun 1, 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 22.
When is the first frost in Alta?
The first hard freeze (28°F) in Alta typically arrives around Sep 29, per NOAA 1991–2020 climate normals — the point tender summer crops finish. Lighter frosts run ahead of it, near Sep 15, so the watching starts about Aug 30 — about 120 days after the spring freeze cleared.
How long is the growing season in Alta?
Measured between 28°F hard freezes, Alta sees about 120 frost-free days — roughly Jun 1 through Sep 29, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer Jun 22 to Sep 15, about 85 days.
Is the soil safe to grow vegetables in Alta?
The federal record around Alta runs heavier than most — 586 documented sites, mostly Mining entries (474), the nearest Mining record about 0.2 miles out — so test the soil before planting food in the ground, and raised beds with clean imported soil grow well in the meantime. Even here, proximity to a documented site is information, not a diagnosis of any one yard; the contamination map shows exactly what's recorded and where.
How do gardeners stretch the season in Alta?
With about 120 frost-free days between hard freezes, Alta 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 148 to 176 days — and cold frames or low tunnels buy more. Starting transplants indoors ahead of the Jun 1 hard-freeze normal stretches the season without touching the calendar.
Everything above is measured at Alta's scale — its 6a band and its 120-day season. Your yard writes its own version of Alta'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 Alta’s own scale
7 of the readings below were taken at Alta's own scale — its own ~120-day season between 28°F freezes, the 2,890 acres it covers and 586 documented sites around it; 4 are borrowed from a wider read, named and linked below.
Measured here
- Alta's own USDA hardiness band, zones 6aUSDA PHZM 2023
- Alta's own 28°F hard-freeze dates, about Jun 1 and Sep 29 and the ~120-day span between themNOAA 1991–2020 Climate Normals
- 586 documented contamination sites on the federal record near Alta, the closest Mining record about 0.2 miles out from the town centreFederal environmental registers
- Alta's boundary and the 2,890 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 6a and a ~120-day seasonGrowable Ground crop-matching engine
- Alta sits in the Wasatch and Uinta Mountains — not the ecoregion its county mostly readsUS EPA Level III Ecoregions
- A documented spotted-lanternfly record within reach of Altalydemapr (De Bona & Helmus), 10 km survey lattice
Inherited from a wider read
- Soil character — no town-scale survey exists, so Alta's 2,890 acres read through its county's SSURGO summaryfrom Salt Lake County
- Growing-degree days and winter chill — measured county-wide only, so the county page carries themfrom Salt Lake County
- The growing challenges every Utah grower plans around — written at state scale, so they stay on the state guidefrom Utah
- Butterfly and beetle records, and the farmland pesticide estimate — all published county-widefrom Salt Lake County
What this page can’t tell you
- The soil pH, drainage, sun hours, and frost pockets on any one lot among Alta's 2,890 acreswhy one lot differs from the next →
- Which side of Alta you're on — a low spot frosts first and a south wall warms early, and one normal is being asked to speak for all 2,890 acresreading your own microclimate →
- How close that record sits to YOUR lot — the closest Mining record about 0.2 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 Alta-wide figureread your own land →
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