Idaho Springs, Colorado, sits in USDA hardiness zone 5b — enough range to grow cool-season vegetables, hardy fruit, and warm-season crops that mature before the first hard frost.
Growers here do well with cabbage, cranberry, lavender, and collard greens — with the usual caveat that any single yard's soil, sun, and drainage cast the deciding vote.
Even in Idaho 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 Idaho 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 Idaho Springs — soil, climate, flood, and parcel records. How we handle your address.
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Idaho Springs — the short answer
Idaho Springs, Colorado: USDA zone 5b, about 139 days between hard freezes, across 2K acres of city.
- USDA zone
- 5b
- USDA PHZM 2023
- Last hard freeze (28°F)
- May 14
- 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
- ~139
- NOAA 1991–2020 Climate Normals, 28°F — this town
- City area
- 2K 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 5b is Idaho Springs's average, not your lot's — a low corner or a tree line moves it. Against Idaho Springs's 139-day season, see what your own ground reads.
Soil varies lot by lot — soil types explained.
What this means for growing in Idaho Springs
Each reading below is measured for Idaho Springs itself — here is what it means for a garden here, and the move an experienced grower makes about it.
Season length
MeasuredIdaho Springs runs about 139 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
MeasuredIdaho Springs sits in USDA hardiness zone 5b.
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 Idaho Springs is in
Idaho Springs sits in the Southern Rockies — EPA Level III, inside the wider Northwestern Forested Mountains. That is read at Idaho Springs's own centroid rather than borrowed from Clear Creek County.
What Grows in Idaho Springs
Every plant below cleared Idaho Springs's own zone 5b and its 139-day season. Each card opens that plant's Colorado profile. How we score.
Is it too late to plant in Idaho Springs?
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 16; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near May 14 (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 Idaho Springs
Closest first, within ~10 miles of Idaho Springs. Listing isn't leaking, and distance isn't exposure.
- Colo. Sch. Mines ClaimsMining · 2100 ft
- Tom Boy, Treasure Vault, John Paul Jones, Edna Fannie, Golden TreasureMining · 2200 ft
- Tom BoyMining · 2200 ft
- ArgoMining · 2400 ft
- Alta #6120Underground Storage Tanks · 0.5 mi
- Former Service StationUnderground Storage Tanks · 0.5 mi
- Blackwell Oil CoUnderground Storage Tanks · 0.6 mi
- Scorpion ShellUnderground Storage Tanks · 0.6 mi
- SAFEWAY STORE #390Brownfields · 0.6 mi
- John Paul JonesMining · 0.6 mi
- Spring Station LLCUnderground Storage Tanks · 0.6 mi
- Idaho Springs Sunmart #501Underground Storage Tanks · 0.6 mi
6 more sites are on the record inside the same radius. See them on the map
Measured from Idaho 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 Idaho Springs.
Sources Checked
within ~10 miles of Idaho Springs
Severity Distribution
within ~10 miles of Idaho Springs
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around Idaho Springs, Mining runs higher than the national average — 603 sites within ~10 miles of Idaho Springs. 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.
Test soil for heavy metals (lead, arsenic, cadmium, mercury) — this is essential near any mining site.
Check your specific parcel in Idaho 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 Idaho Springs average
Your land is one point inside Idaho Springs
Everything above resolves to Idaho Springs as a whole — one PHZM band and one 28°F frost record, read across 2K 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 city 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 Idaho Springs Average
Idaho Springs Average
- ●USDA Zones 5b, averaged across Idaho Springs
- ●One soil character for all of Idaho Springs
- ●Frost dates read at Idaho Springs's scale: May 14 to Sep 30
YOUR Parcel
- ✓Your exact zone, not Idaho Springs's 5b
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your specific parcel in Idaho Springs
Pull a site-specific report for your exact address in Idaho Springs, Colorado — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Idaho Springs averages can't show:
We read public map data around Idaho Springs — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Idaho Springs average
How we know this about Idaho Springs
The datasets: hardiness from the USDA ARS Plant Hardiness Zone Map 2023, read at this city’s own centroid; hard-freeze dates from NOAA 1991–2020 28°F normals at Idaho 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 city grain anywhere on this page — there is no city-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 Idaho Springs
When does frost risk typically end in Idaho Springs?
The last hard freeze (28°F) in Idaho Springs typically lands around May 14, 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 4.
When is the first frost in Idaho Springs?
The first hard freeze (28°F) in Idaho Springs 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 139 days after the spring freeze cleared.
How long is the growing season in Idaho Springs?
Measured between 28°F hard freezes, Idaho Springs sees about 139 frost-free days — roughly May 14 through Sep 30, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer Jun 4 to Sep 16, about 104 days.
Is the soil safe to grow vegetables in Idaho Springs?
The federal record around Idaho Springs runs heavier than most — 712 documented sites, mostly Mining entries (603), the nearest Mining record about 0.4 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 Idaho Springs?
With about 139 frost-free days between hard freezes, Idaho 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 167 to 195 days — and cold frames or low tunnels buy more. Starting transplants indoors ahead of the May 14 hard-freeze normal stretches the season without touching the calendar.
Everything above is measured at Idaho Springs's scale — its 5b band and its 139-day season. Your yard writes its own version of Idaho 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 Idaho Springs’s own scale
6 of the readings below were taken at Idaho Springs's own scale — its own ~139-day season between 28°F freezes, the 1,526 acres it covers and 712 documented sites around it; 4 are borrowed from a wider read, named and linked below.
Measured here
- Idaho Springs's own USDA hardiness band, zones 5bUSDA PHZM 2023
- Idaho Springs's own 28°F hard-freeze dates, about May 14 and Sep 30 and the ~139-day span between themNOAA 1991–2020 Climate Normals
- 712 documented contamination sites on the federal record near Idaho Springs, the closest Mining record about 0.4 miles out from the town centreFederal environmental registers
- Idaho Springs's boundary and the 1,526 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 5b and a ~139-day seasonGrowable Ground crop-matching engine
- The ecoregion at Idaho Springs's own centroid, the Southern RockiesUS EPA Level III Ecoregions
Inherited from a wider read
- Soil character — no town-scale survey exists, so Idaho Springs's 1,526 acres read through its county's SSURGO summaryfrom Clear Creek County
- Growing-degree days and winter chill — measured county-wide only, so the county page carries themfrom Clear Creek 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 Clear Creek County
What this page can’t tell you
- The soil pH, drainage, sun hours, and frost pockets on any one lot among Idaho Springs's 1,526 acreswhy one lot differs from the next →
- Which side of Idaho 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 1,526 acresreading your own microclimate →
- How close that record sits to YOUR lot — the closest Mining record about 0.4 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 Idaho Springs-wide figureread your own land →