Gunbarrel, Colorado, sits in USDA hardiness zone 6a — a band that supports both cool-season staples and warm-season crops chosen to fit the local frost window.
A short list that earns its place here — cabbage, blackberry, california poppy, and collard greens — with any one site's soil, sun, and drainage making the final cut.
Even in Gunbarrel, 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 Gunbarrel 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 Gunbarrel — soil, climate, flood, and parcel records. How we handle your address.
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Gunbarrel — the short answer
Gunbarrel, Colorado: USDA zone 6a, about 180 days between hard freezes, across 4K acres of town.
- USDA zone
- 6a
- USDA PHZM 2023
- Last hard freeze (28°F)
- Apr 20
- NOAA 1991–2020 Climate Normals, 28°F — this town
- First hard freeze (28°F)
- Oct 17
- NOAA 1991–2020 Climate Normals, 28°F — this town
- Days between freezes
- ~180
- NOAA 1991–2020 Climate Normals, 28°F — this town
- Town area
- 4K 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 Gunbarrel's average, not your lot's — a low corner or a tree line moves it. Against Gunbarrel's 180-day season, see what your own ground reads.
Your town runs its own season
Gunbarrel's own 30-year record measures about 180 days between 28°F killing freezes — 38 days longer than Boulder County's ~142. Both are measured records, not estimates.
That gap is the whole reason a county average can mislead here. Plant against Gunbarrel's ~180-day season rather than the county figure — and the sun, slope and cold-air drainage on your specific lot move it again.
NOAA Regional Climate Centers ACIS (1991–2020), 30-year daily minimum record. Both figures are measured records — this town’s own and its county’s. A town with no record of its own is absent here rather than estimated.
Soil varies lot by lot — soil types explained.
What this means for growing in Gunbarrel
Each reading below is measured for Gunbarrel itself — here is what it means for a garden here, and the move an experienced grower makes about it.
Season length
MeasuredGunbarrel runs about 180 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
MeasuredGunbarrel 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 Gunbarrel is in
Gunbarrel sits in the High Plains — EPA Level III, inside the wider Great Plains. That is read at Gunbarrel's own centroid, and it is not what its county reads: Boulder County is mostly Southern Rockies. The wider page above you is answering a different question about different ground.
What Grows in Gunbarrel
Every plant below cleared Gunbarrel's own zone 6a and its 180-day season. Each card opens that plant's Colorado profile. How we score.
Is it too late to plant in Gunbarrel?
Usually not — gardeners here simply switch what goes in the ground as the season moves. Cool-season crops can go in from around Mar 23; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near Apr 20 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Oct 17 — long-season crops need about 90 days of runway, quick greens only 30. As the window narrows, the plantings just get faster — fall brassicas, then greens, then garlic to finish.
What's on the federal record near Gunbarrel
Closest first, within ~10 miles of Gunbarrel. Listing isn't leaking, and distance isn't exposure.
- DIETERICH STANDARD INCBrownfields · 1.3 mi
- DIETERICH STANDARD INCToxics Release Inventory · 1.3 mi
- 75TH STREET WASTEWATER TREATMENT PLANTBrownfields · 1.3 mi
- SB00106907AAAA SITE C44Nitrate · 1.3 mi
- Micro Motion Inc - 80k Flow FacilityUnderground Storage Tanks · 1.4 mi
- CLEARCUT RESEARCHBrownfields · 1.4 mi
- MICRO MOTION INC - 7070 WINCHESTER CIRBrownfields · 1.4 mi
- MICRO MOTION INC - 7070 WINCHESTER CIRToxics Release Inventory · 1.4 mi
- WESTERN MOBILE BOULDER INCBrownfields · 1.5 mi
- SB00107024BAAC SITE C68Nitrate · 1.5 mi
- Boulder County Road District #1Underground Storage Tanks · 1.6 mi
- DESIGN FABRICATORS INCBrownfields · 1.6 mi
6 more sites are on the record inside the same radius. See them on the map
Measured from Gunbarrel'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 Gunbarrel.
Sources Checked
within ~10 miles of Gunbarrel
Severity Distribution
within ~10 miles of Gunbarrel
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around Gunbarrel, Toxics Release Inventory runs higher than the national average — 66 sites within ~10 miles of Gunbarrel. Knowing it is half the work — and it's nothing a thoughtful grower can't plan for.
Toxics Release Inventory: TRI facilities report annual chemical releases to air, water, and land.
Check prevailing wind direction — downwind parcels face higher exposure than upwind or crosswind locations.
Check your specific parcel in Gunbarrel
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 Gunbarrel average
Your land is one point inside Gunbarrel
Everything above resolves to Gunbarrel as a whole — and this is a town whose own 30-year record already runs a season its county’s does not. Your parcel sits at one point inside even that. 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 Gunbarrel Average
Gunbarrel Average
- ●USDA Zones 6a, averaged across Gunbarrel
- ●One soil character for all of Gunbarrel
- ●Frost dates read at Gunbarrel's scale: Apr 20 to Oct 17
YOUR Parcel
- ✓Your exact zone, not Gunbarrel's 6a
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your specific parcel in Gunbarrel
Pull a site-specific report for your exact address in Gunbarrel, Colorado — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Gunbarrel averages can't show:
We read public map data around Gunbarrel — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Gunbarrel average
How we know this about Gunbarrel
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 Gunbarrel’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 Gunbarrel
When does frost risk typically end in Gunbarrel?
The last hard freeze (28°F) in Gunbarrel typically lands around Apr 20, 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 11.
When is the first frost in Gunbarrel?
The first hard freeze (28°F) in Gunbarrel typically arrives around Oct 17, per NOAA 1991–2020 climate normals — the point tender summer crops finish. Lighter frosts run ahead of it, near Oct 3, so the watching starts about Sep 17 — about 180 days after the spring freeze cleared.
How long is the growing season in Gunbarrel?
Measured between 28°F hard freezes, Gunbarrel sees about 180 frost-free days — roughly Apr 20 through Oct 17, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer May 11 to Oct 3, about 145 days.
Is the soil safe to grow vegetables in Gunbarrel?
The federal record around Gunbarrel is a meaningful one — 1,011 documented sites, mostly Underground Storage Tanks entries (408), the nearest Brownfields record about 1.3 miles 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 Gunbarrel?
From about Sep 17 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 17 (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 17. Hardy greens and roots shrug off light frost and sweeten after it — leave them in.
Everything above is measured at Gunbarrel's scale — its 6a band and its 180-day season. Your yard writes its own version of Gunbarrel'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 Gunbarrel’s own scale
6 of the readings below were taken at Gunbarrel's own scale — its own ~180-day season between 28°F freezes, the 3,997 acres it covers and 1,011 documented sites around it; 4 are borrowed from a wider read, named and linked below.
Measured here
- Gunbarrel's own USDA hardiness band, zones 6aUSDA PHZM 2023
- Gunbarrel's own 28°F hard-freeze dates, about Apr 20 and Oct 17 and the ~180-day span between themNOAA 1991–2020 Climate Normals
- 1,011 documented contamination sites on the federal record near Gunbarrel, the closest Brownfields record about 1.3 miles out from the town centreFederal environmental registers
- Gunbarrel's boundary and the 3,997 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 6a and a ~180-day seasonGrowable Ground crop-matching engine
- Gunbarrel sits in the High 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 Gunbarrel's 3,997 acres read through its county's SSURGO summaryfrom Boulder County
- Growing-degree days and winter chill — measured county-wide only, so the county page carries themfrom Boulder 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 Boulder County
What this page can’t tell you
- The soil pH, drainage, sun hours, and frost pockets on any one lot among Gunbarrel's 3,997 acreswhy one lot differs from the next →
- Which side of Gunbarrel you're on — a low spot frosts first and a south wall warms early, and one normal is being asked to speak for all 3,997 acresreading your own microclimate →
- How close that record sits to YOUR lot — the closest Brownfields record about 1.3 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 Gunbarrel-wide figureread your own land →
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