Silverton, Colorado, sits in USDA hardiness zone 4b — a band that supports both cool-season staples and warm-season crops chosen to fit the local frost window.
Well-matched crops include zucchini, cranberry, cilantro, and okra, and the gap between "grows in the area" and "grows in your yard" is closed by soil, sun, and drainage.
Even in Silverton, 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 Silverton 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 Silverton — soil, climate, flood, and parcel records. How we handle your address.
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Silverton — the short answer
Silverton, Colorado: USDA zone 4b, about 98 days between hard freezes, across 534 acres of town.
- USDA zone
- 4b
- USDA PHZM 2023
- Last hard freeze (28°F)
- Jun 10
- NOAA 1991–2020 Climate Normals, 28°F — this town
- First hard freeze (28°F)
- Sep 16
- NOAA 1991–2020 Climate Normals, 28°F — this town
- Days between freezes
- ~98
- NOAA 1991–2020 Climate Normals, 28°F — this town
- Town area
- 534 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 Silverton's average, not your lot's — a low corner or a tree line moves it. Against Silverton's 98-day season, see what your own ground reads.
Soil varies lot by lot — soil types explained.
What this means for growing in Silverton
Each reading below is measured for Silverton itself — here is what it means for a garden here, and the move an experienced grower makes about it.
Season length
MeasuredSilverton runs about 98 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
MeasuredSilverton 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 Silverton is in
Silverton sits in the Southern Rockies — EPA Level III, inside the wider Northwestern Forested Mountains. That is read at Silverton's own centroid rather than borrowed from San Juan County.
What Grows in Silverton
Every plant below cleared Silverton's own zone 4b and its 98-day season. Each card opens that plant's Colorado profile. How we score.
Is it too late to plant in Silverton?
For most of the year, no — what changes is which crops still fit the days remaining. Cool-season crops can go in from around May 13; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near Jun 10 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Sep 16 — 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 Silverton
Closest first, within ~10 miles of Silverton. Listing isn't leaking, and distance isn't exposure.
- DoraMining · 100 ft
- San Juan ServicesUnderground Storage Tanks · 350 ft
- Carriage House Public WorksUnderground Storage Tanks · 350 ft
- Silverton GroceryUnderground Storage Tanks · 350 ft
- San Juan County Garage & ShopUnderground Storage Tanks · 350 ft
- ROOT AND NORTON LABORATORYBrownfields · 350 ft
- Triangle MotelUnderground Storage Tanks · 1000 ft
- CDOT SilvertonUnderground Storage Tanks · 1700 ft
- Town Of SilvertonUnderground Storage Tanks · 1800 ft
- COLORADO DEPT OF HWYS - SILVERTONBrownfields · 1900 ft
- Corning Wonder MineMining · 2300 ft
- Unknown GroupMining · 0.5 mi
6 more sites are on the record inside the same radius. See them on the map
Measured from Silverton'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 Silverton.
Sources Checked
within ~10 miles of Silverton
Severity Distribution
within ~10 miles of Silverton
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around Silverton, two things run higher than the national average within ~10 miles of Silverton — Mining (607 sites) and Superfund (13 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.
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 Silverton
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 Silverton average
Your land is one point inside Silverton
Everything above resolves to Silverton as a whole — one PHZM band and one 28°F frost record, read across 534 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 Silverton Average
Silverton Average
- ●USDA Zones 4b, averaged across Silverton
- ●One soil character for all of Silverton
- ●Frost dates read at Silverton's scale: Jun 10 to Sep 16
YOUR Parcel
- ✓Your exact zone, not Silverton's 4b
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your specific parcel in Silverton
Pull a site-specific report for your exact address in Silverton, Colorado — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Silverton averages can't show:
We read public map data around Silverton — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Silverton average
How we know this about Silverton
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 Silverton’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 Silverton
When does frost risk typically end in Silverton?
The last hard freeze (28°F) in Silverton typically lands around Jun 10, 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 Jul 1.
When is the first frost in Silverton?
The first hard freeze (28°F) in Silverton typically arrives around Sep 16, per NOAA 1991–2020 climate normals — the point tender summer crops finish. Lighter frosts run ahead of it, near Sep 2, so the watching starts about Aug 17 — about 98 days after the spring freeze cleared.
How long is the growing season in Silverton?
Measured between 28°F hard freezes, Silverton sees about 98 frost-free days — roughly Jun 10 through Sep 16, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer Jul 1 to Sep 2, about 63 days.
Is the soil safe to grow vegetables in Silverton?
The federal record around Silverton runs heavier than most — 631 documented sites, mostly Mining entries (607), the nearest Mining record under a tenth of a mile 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 Silverton?
With about 98 frost-free days between hard freezes, Silverton 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 126 to 154 days — and cold frames or low tunnels buy more. Starting transplants indoors ahead of the Jun 10 hard-freeze normal stretches the season without touching the calendar.
Everything above is measured at Silverton's scale — its 4b band and its 98-day season. Your yard writes its own version of Silverton'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 Silverton’s own scale
6 of the readings below were taken at Silverton's own scale — its own ~98-day season between 28°F freezes, the 534 acres it covers and 631 documented sites around it; 4 are borrowed from a wider read, named and linked below.
Measured here
- Silverton's own USDA hardiness band, zones 4bUSDA PHZM 2023
- Silverton's own 28°F hard-freeze dates, about Jun 10 and Sep 16 and the ~98-day span between themNOAA 1991–2020 Climate Normals
- 631 documented contamination sites on the federal record near Silverton, the closest Mining record under a tenth of a mile out from the town centreFederal environmental registers
- Silverton's boundary and the 534 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 4b and a ~98-day seasonGrowable Ground crop-matching engine
- The ecoregion at Silverton's own centroid, the Southern RockiesUS EPA Level III Ecoregions
Inherited from a wider read
- Soil character — no town-scale survey exists, so Silverton's 534 acres read through its county's SSURGO summaryfrom San Juan County
- Growing-degree days and winter chill — measured county-wide only, so the county page carries themfrom San Juan County
- The growing challenges every Colorado grower plans around — written at state scale, so they stay on the state guidefrom Colorado
- Butterfly and beetle records, and the farmland pesticide estimate — all published county-widefrom San Juan County
What this page can’t tell you
- The soil pH, drainage, sun hours, and frost pockets on any one lot among Silverton's 534 acreswhy one lot differs from the next →
- Which side of Silverton you're on — a low spot frosts first and a south wall warms early, and one normal is being asked to speak for all 534 acresreading your own microclimate →
- How close that record sits to YOUR lot — the closest Mining 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 Silverton-wide figureread your own land →