Granby, Colorado, sits in USDA hardiness zone 4a — a band that supports both cool-season staples and warm-season crops chosen to fit the local frost window.
Among the crops suited to this profile: okra, cranberry, cilantro, and zucchini. The site-level story — soil, sun, drainage — decides the rest.
Even in Granby, 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 Granby 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 Granby — soil, climate, flood, and parcel records. How we handle your address.
No card required · your full report in seconds
Granby — the short answer
Granby, Colorado: USDA zone 4a, about 110 days between hard freezes, across 8K acres of town.
- USDA zone
- 4a
- USDA PHZM 2023
- Last hard freeze (28°F)
- May 31
- NOAA 1991–2020 Climate Normals, 28°F — this town
- First hard freeze (28°F)
- Sep 18
- NOAA 1991–2020 Climate Normals, 28°F — this town
- Days between freezes
- ~110
- NOAA 1991–2020 Climate Normals, 28°F — this town
- Town area
- 8K 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 4a is Granby's average, not your lot's — a low corner or a tree line moves it. Against Granby's 110-day season, see what your own ground reads.
Soil varies lot by lot — soil types explained.
What this means for growing in Granby
Each reading below is measured for Granby itself — here is what it means for a garden here, and the move an experienced grower makes about it.
Season length
MeasuredGranby runs about 110 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
MeasuredGranby sits in USDA hardiness zone 4a.
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 Granby is in
Granby sits in the Southern Rockies — EPA Level III, inside the wider Northwestern Forested Mountains. That is read at Granby's own centroid rather than borrowed from Grand County.
What Grows in Granby
Every plant below cleared Granby's own zone 4a and its 110-day season. Each card opens that plant's Colorado profile. How we score.
Is it too late to plant in Granby?
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 3; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near May 31 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Sep 18 — 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's on the federal record near Granby
Closest first, within ~10 miles of Granby. Listing isn't leaking, and distance isn't exposure.
- Owl Ridge Rr 210670Underground Storage Tanks · 1900 ft
- Barn StoreUnderground Storage Tanks · 1900 ft
- Granby YardUnderground Storage Tanks · 1900 ft
- City Market Fueling #246Underground Storage Tanks · 2400 ft
- CITY MARKET 446Brownfields · 0.5 mi
- THOMAS A MASON CO INCBrownfields · 0.6 mi
- MIDDLE PARK HEALTHBrownfields · 0.8 mi
- Granby Mini-MartUnderground Storage Tanks · 1.6 mi
- Granby Heating & Sheet Metal IncUnderground Storage Tanks · 1.6 mi
- 6t6 Self ServeUnderground Storage Tanks · 1.6 mi
- 7-Eleven #18589Underground Storage Tanks · 1.6 mi
- Joes SinclairUnderground Storage Tanks · 1.6 mi
6 more sites are on the record inside the same radius. See them on the map
Measured from Granby'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 Granby.
Total Sites
103
within ~10 miles of Granby
Risk Level
Elevated
Highest-severity
1 Superfund site (none NPL-listed)
Sources Checked
within ~10 miles of Granby
Severity Distribution
within ~10 miles of Granby
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around Granby, Nitrate runs higher than the national average — 44 sites within ~10 miles of Granby. Knowing it is half the work — and it's nothing a thoughtful grower can't plan for.
Nitrate: Nitrate contamination primarily comes from agricultural fertilizer runoff and failing septic systems.
Test well water for nitrate if you rely on a private well for irrigation (EPA standard: 10 mg/L).
Check your specific parcel in Granby
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 Granby average
Your land is one point inside Granby
Everything above resolves to Granby as a whole — one PHZM band and one 28°F frost record, read across 8K 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 Granby Average
Granby Average
- ●USDA Zones 4a, averaged across Granby
- ●One soil character for all of Granby
- ●Frost dates read at Granby's scale: May 31 to Sep 18
YOUR Parcel
- ✓Your exact zone, not Granby's 4a
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your specific parcel in Granby
Pull a site-specific report for your exact address in Granby, Colorado — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Granby averages can't show:
We read public map data around Granby — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Granby average
How we know this about Granby
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 Granby’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 Granby
When does frost risk typically end in Granby?
The last hard freeze (28°F) in Granby typically lands around May 31, 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 21.
When is the first frost in Granby?
The first hard freeze (28°F) in Granby typically arrives around Sep 18, per NOAA 1991–2020 climate normals — the point tender summer crops finish. Lighter frosts run ahead of it, near Sep 4, so the watching starts about Aug 19 — about 110 days after the spring freeze cleared.
How long is the growing season in Granby?
Measured between 28°F hard freezes, Granby sees about 110 frost-free days — roughly May 31 through Sep 18, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer Jun 21 to Sep 4, about 75 days.
Is the soil safe to grow vegetables in Granby?
The federal record around Granby is a meaningful one — 103 documented sites, mostly Underground Storage Tanks entries (45), the nearest Underground Storage Tanks record about 0.4 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 gardeners stretch the season in Granby?
With about 110 frost-free days between hard freezes, Granby 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 138 to 166 days — and cold frames or low tunnels buy more. Starting transplants indoors ahead of the May 31 hard-freeze normal stretches the season without touching the calendar.
Everything above is measured at Granby's scale — its 4a band and its 110-day season. Your yard writes its own version of Granby'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 Granby’s own scale
6 of the readings below were taken at Granby's own scale — its own ~110-day season between 28°F freezes, the 8,116 acres it covers and 103 documented sites around it; 4 are borrowed from a wider read, named and linked below.
Measured here
- Granby's own USDA hardiness band, zones 4aUSDA PHZM 2023
- Granby's own 28°F hard-freeze dates, about May 31 and Sep 18 and the ~110-day span between themNOAA 1991–2020 Climate Normals
- 103 documented contamination sites on the federal record near Granby, the closest Underground Storage Tanks record about 0.4 miles out from the town centreFederal environmental registers
- Granby's boundary and the 8,116 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 4a and a ~110-day seasonGrowable Ground crop-matching engine
- The ecoregion at Granby's own centroid, the Southern RockiesUS EPA Level III Ecoregions
Inherited from a wider read
- Soil character — no town-scale survey exists, so Granby's 8,116 acres read through its county's SSURGO summaryfrom Grand County
- Growing-degree days and winter chill — measured county-wide only, so the county page carries themfrom Grand 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 Grand County
What this page can’t tell you
- The soil pH, drainage, sun hours, and frost pockets on any one lot among Granby's 8,116 acreswhy one lot differs from the next →
- Which side of Granby you're on — a low spot frosts first and a south wall warms early, and one normal is being asked to speak for all 8,116 acresreading your own microclimate →
- How close that record sits to YOUR lot — the closest Underground Storage Tanks 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 Granby-wide figureread your own land →