Summit County, in Colorado, sits in USDA hardiness zone 5b — a range where zone-matched perennials and frost-aware annual timing set what succeeds.
On paper, pumpkin, blackberry, lavender, and zucchini all suit these conditions — on the ground, soil, sun, and drainage make the final call.
Summit County lies within the Colorado High Country (Central Rockies) — a regional growing area with its own character.
Grounded in USDA PHZM 2023 · Growable Ground suitability scoring · NOAA 1991–2020 Climate Normals
Summit County holds more than one microclimate.
Soils and elevations shift across Summit County, so your frost dates and drainage aren't the county average. 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 Summit County — soil, climate, flood, and parcel records. How we handle your address.
No card required · your full report in seconds
Summit County — the short answer
Summit County, Colorado: USDA zone 5b, about 102 days between hard freezes, across 389K acres.
- USDA zone
- 5b
- USDA PHZM 2023
- Last hard freeze (28°F)
- Jun 7
- NOAA 1991–2020 Climate Normals, 28°F
- First hard freeze (28°F)
- Sep 17
- NOAA 1991–2020 Climate Normals, 28°F
- Days between freezes
- ~102
- NOAA 1991–2020 Climate Normals, 28°F
- County area
- 389K acres
- US Census TIGER/Line 2025
Every figure names the dataset it came from. Hard-freeze dates are county 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 Summit County's average, not your lot's — a low corner or a tree line moves it. Against Summit County's 102-day season, see what your own ground reads.
Heat in Summit County
Across a year, Summit County accumulates about 296 growing degree days above 50°F, about 1,536 fewer than the middle Colorado county — ahead of 6 of Colorado’s 64 counties. Degree days are the heat a crop actually gets to work with — more of them is more room to ripen a long-season crop before the freeze closes the window.
Grounded in PRISM Climate Group, Oregon State University — 1991–2020 monthly normals
Soil in Summit County
Across Summit County, the ground is predominantly Mollisols, where Frisco, Grenadier, and Peeler are the most extensive named soil series. The soil is generally well drained with a sandy loam surface. Topsoil pH runs about 6.2–7.0, neutral. Rainfall drains through hydrologic group B soils.
Soil order
Mollisols
Drainage
Well drained
Hydric soils
6%
Soil still varies lot by lot — soil types explained.
How the ground varies across Summit County
The USDA soil survey maps 80% of Summit County as well drained — but another 5% drains differently: 5% poorly drained.
Frisco is the most extensive named soil at 22% of mapped acres, then Grenadier (14%) and Peeler (12%).
Which of them your own lot sits on is a parcel question, not a county one. Check your address for the survey at your boundary.
What this means for growing in Summit County
Each reading below is measured for Summit County itself — here is what it means for a garden here, and the move an experienced grower makes about it.
Drainage
MeasuredThe dominant soils across Summit County are well drained, in hydrologic group B — ground that drains quickly.
The upside is soil you can work early in spring and roots that never drown; the cost is that fast-draining ground dries out fast and leaches nutrients away before plants can use them.
Work in compost and mulch to hold moisture and feed, and water more often in short doses than deep and rarely.
USDA NRCS SSURGO
Surface pH
MeasuredTopsoil across Summit County runs about pH 6.2–7.0, close to neutral.
This is the range most vegetables prefer — one correction you probably do not have to make, which is genuinely good news for a new bed.
Keep it there with compost rather than lime or sulfur, and only amend if your own soil test says otherwise.
USDA NRCS SSURGO
Season length
MeasuredSummit County runs about 102 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
MeasuredSummit County 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 Summit County is in
Summit County sits in the Southern Rockies — EPA Level III, inside the wider Northwestern Forested Mountains. One consistent ecological setting across the whole county.
What Grows in Summit County
We scored all 1,086 plants against Summit County's own USDA zone 5b and its own 102-day season between hard freezes, using the same matching engine that runs a full parcel report. These cleared both. Sun, soil pH and drainage vary lot by lot — those are the parcel questions below. Each card opens that plant's Colorado profile.
Is it too late to plant in Summit County?
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 May 10; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near Jun 7 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Sep 17 — long-season crops need about 90 days of runway, quick greens only 30. When the window is tight, the fall moves are quick ones — baby greens, radishes, and garlic set for next season.
What gets applied to farmland in Summit County
USGS estimates 9 lb of Glyphosate on Summit County farmland in 2019, its largest by weight, ahead of Chlorpyrifos (8 lb) and Dimethoate (5 lb).
Farmland across the whole county, not any one lot. Check your address for the site-by-site record.
Safe to Grow Here?
What the federal record shows across Summit County — and how to grow with it.
We checked the federal record across Summit County — 493 documented sites across 7 of the 9 source types we track.
The most significant on record: 9 Superfund sites (none NPL-listed). Sites tracked in EPA's Superfund program — from assessment-stage CERCLIS entries to confirmed National Priorities List cleanup sites.
Summit County carries one of the heavier federal records we track — and that's not a verdict on your yard. Proximity to a documented site is information, not a diagnosis: nothing here says any particular parcel is affected. It does earn one concrete step — before food beds go in the ground, a professional soil test tells you exactly what you're working with, and raised beds with clean imported soil grow well almost anywhere in the meantime.
Sources: EPA, USGS — 1.8M documented sites tracked nationwide across 9 federal source types.
What's on the federal record near Summit County
Closest first, across Summit County. Listing isn't leaking, and distance isn't exposure.
- COLORADO DEPT OF TRANS - FRISCOBrownfields · 3.0 mi
- CDOT FriscoUnderground Storage Tanks · 3.0 mi
- Kum & Go #0948Underground Storage Tanks · 3.0 mi
- Eleanor H Greer PropertyUnderground Storage Tanks · 3.0 mi
- CST Metro LLC DBA Corner Store #633Underground Storage Tanks · 3.0 mi
- SAFEWAY STORE #836Brownfields · 3.1 mi
- Ski Country ShellUnderground Storage Tanks · 3.1 mi
- Frisco ConocoUnderground Storage Tanks · 3.2 mi
- 7-Eleven #17284Underground Storage Tanks · 3.2 mi
- COLORADO DEPT OF TRANS - A BASINBrownfields · 3.2 mi
- SALLY BEAUTY SUPPLY #10446Brownfields · 3.2 mi
- Antlers General StoreUnderground Storage Tanks · 3.2 mi
6 more sites are on the record inside the same radius. See them on the map
Measured from Summit County'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 Summit County.
Sources Checked
across Summit County
Severity Distribution
across Summit County
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around Summit County, two things run higher than the national average across Summit County — Mining (332 sites) and Superfund (9 sites). That's not a problem with your land — it's information about 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 Summit County
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 Summit County average
Your land is one point inside Summit County
Everything above resolves to Summit County as a whole — one PHZM band and one county frost record, read across 389K 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 county 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 county average.
Your Lot vs the Summit County Average
Summit County Average
- ●USDA Zones 5b, averaged across Summit County
- ●One soil character for all of Summit County
- ●Frost dates read at Summit County's scale: Jun 7 to Sep 17
YOUR Parcel
- ✓Your exact zone, not Summit County's 5b
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your parcel in Summit County
Pull a site-specific report for your exact address in Summit County, Colorado — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Summit County averages can't show:
We read public map data around Summit County — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Summit County average
How we know this about Summit County
The datasets: hardiness from the USDA ARS Plant Hardiness Zone Map 2023, read at county grain; hard-freeze dates from NOAA 1991–2020 28°F normals at this county’s own record where one resolves, and the labelled statewide window where none does; soils from the USDA NRCS SSURGO survey, area-weighted across the county’s own map units; boundaries and acreage from US Census TIGER/Line 2025; the contamination and pesticide records from the federal sources named in their beats above. Where Summit County carries no record of its own, the figure is inherited and labelled — the resolution ledger below names each.
Common questions about Summit County
When does frost risk typically end in Summit County?
The last hard freeze (28°F) in Summit County typically lands around Jun 7, 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 28.
How long is the growing season in Summit County?
Measured between 28°F hard freezes, Summit County sees about 102 frost-free days — roughly Jun 7 through Sep 17, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer Jun 28 to Sep 3, about 67 days.
Is the soil safe to grow vegetables in Summit County?
The federal record around Summit County runs heavier than most — 493 documented sites, mostly Mining entries (332), the nearest Brownfields record about 3.0 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 Summit County?
With about 102 frost-free days between hard freezes, Summit County 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 130 to 158 days — and cold frames or low tunnels buy more. Starting transplants indoors ahead of the Jun 7 hard-freeze normal stretches the season without touching the calendar.
Everything above is measured at Summit County's scale — its 5b band and its 102-day season. Your yard writes its own version of Summit County's numbers: we read soil, sun, drainage and frost at your exact address. Try it for 14 days — no card required.
Will It Grow Here?
Zone fit is the first question — each answer below reads Colorado's frost window, season length, and soil profile against the plant's real requirements.
What this page reads at Summit County’s own scale
8 of the readings below were taken at Summit County's own scale — its own ~102-day span between 28°F freezes, the 3 most extensive soil series mapped here and 493 documented sites inside its boundary; one is borrowed from a wider read, named and linked below.
Measured here
- Summit County's own USDA hardiness band, zones 5bUSDA PHZM 2023
- Summit County's own 28°F hard-freeze dates and its ~102-day span between themNOAA 1991–2020 Climate Normals
- The soil order, drainage, surface pH, and the 3 most extensive named soil series mapped in Summit CountyUSDA NRCS SSURGO
- 493 documented contamination sites inside the county boundary, distance-sorted from its center — the closest Brownfields record about 3.0 miles outFederal environmental registers
- Summit County's boundary and the 389,330 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 5b and a ~102-day seasonGrowable Ground crop-matching engine
- Summit County sitting wholly inside the Southern RockiesUS EPA Level III Ecoregions
- Which agricultural compounds go onto Summit County farmland, and roughly how muchUSGS NAWQA EPest county estimates
Inherited from a wider read
- The growing challenges every Colorado grower plans around — written at state scale, so they stay on the state guidefrom Colorado
What this page can’t tell you
- How the season shifts across Summit County — the ~102 days above is one reading at its centre; the 12 towns below each carry their owntowns in this county →
- The soil pH, drainage, sun hours, and frost pockets on any one lot among Summit County's 389,330 acreswhy one lot differs from the next →
- Which of those 493 documented sites actually reaches your soil — that needs your address, the wind, and the groundwater directionhow we read the record →
- Where cold air settles, which slopes face the sun, and which way the wind runs on your own ground — none of it survives being averaged over Summit Countyread your own land →