Colby, Kansas, sits in USDA hardiness zone 6a — 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, hazelnut, lavender, and collard greens — with the usual caveat that any single yard's soil, sun, and drainage cast the deciding vote.
Even in Colby, 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 Colby 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 Colby — soil, climate, flood, and parcel records. How we handle your address.
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Colby — the short answer
Colby, Kansas: USDA zone 6a, about 181 days between hard freezes, across 2K acres of city.
- 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 18
- NOAA 1991–2020 Climate Normals, 28°F — this town
- Days between freezes
- ~181
- 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 6a is Colby's average, not your lot's — a low corner or a tree line moves it. Against Colby's 181-day season, see what your own ground reads.
Soil varies lot by lot — soil types explained.
What this means for growing in Colby
Each reading below is measured for Colby itself — here is what it means for a garden here, and the move an experienced grower makes about it.
Season length
MeasuredColby runs about 181 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
MeasuredColby 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 Colby is in
Colby sits in the High Plains — EPA Level III, inside the wider Great Plains. That is read at Colby's own centroid rather than borrowed from Thomas County.
What Grows in Colby
Every plant below cleared Colby's own zone 6a and its 181-day season. Each card opens that plant's Kansas profile. How we score.
Is it too late to plant in Colby?
Rarely: the season closes in stages, not all at once, and each stage has its crops. 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 18 — long-season crops need about 90 days of runway, quick greens only 30. Late in the year the fall bench takes over — quick greens, radishes, and garlic that repays you next summer.
Documented around Colby
Survey cells within 31 miles of Colby checked for spotted lanternfly, none carrying a detection — a surveyed negative, not an absence of looking. Nearest documented record 548 miles off. What to watch for.
What's on the federal record near Colby
Closest first, within ~10 miles of Colby. Listing isn't leaking, and distance isn't exposure.
- BUTTERFIELD INCUnderground Storage Tanks · 1200 ft
- MURFIN DRILLING INCBrownfields · 1400 ft
- TARBET CONSTR CO INCBrownfields · 1400 ft
- TARBET CONSTR CO INCUnderground Storage Tanks · 1400 ft
- GOLDEN PLAINS AGRICLTURAL TECHUnderground Storage Tanks · 1700 ft
- CITIZEN'S HEALTH MEDICAL CENTERBrownfields · 1800 ft
- UNITED PARCEL SERVICEUnderground Storage Tanks · 1900 ft
- UNITED PARCEL SERVICE INCBrownfields · 2000 ft
- CITIZENS MEDICAL CENTERUnderground Storage Tanks · 2200 ft
- SCHWAN'S SALES OF NORTHWESTERNUnderground Storage Tanks · 2200 ft
- WHOLESALE BEVERAGE CO.Underground Storage Tanks · 2300 ft
- MURFIN DRILLING CO INCBrownfields · 2500 ft
6 more sites are on the record inside the same radius. See them on the map
Measured from Colby'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 Colby.
Sources Checked
within ~10 miles of Colby
Severity Distribution
within ~10 miles of Colby
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around Colby, two things run higher than the national average within ~10 miles of Colby — CAFO (5 sites) and Nitrate (58 sites). It's not cause for alarm — it's worth knowing, and there's a sensible way to grow around it.
CAFO: CAFOs pose a different contamination profile than chemical sources.
Nitrate: Nitrate contamination primarily comes from agricultural fertilizer runoff and failing septic systems.
Wash all produce consumed raw thoroughly, especially leafy greens grown near CAFOs.
Test well water for nitrate if you rely on a private well for irrigation (EPA standard: 10 mg/L).
Check your specific parcel in Colby
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 Colby average
Your land is one point inside Colby
Everything above resolves to Colby 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 Colby Average
Colby Average
- ●USDA Zones 6a, averaged across Colby
- ●One soil character for all of Colby
- ●Frost dates read at Colby's scale: Apr 20 to Oct 18
YOUR Parcel
- ✓Your exact zone, not Colby's 6a
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your specific parcel in Colby
Pull a site-specific report for your exact address in Colby, Kansas — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Colby averages can't show:
We read public map data around Colby — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Colby average
How we know this about Colby
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 Colby’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 Colby
When does frost risk typically end in Colby?
The last hard freeze (28°F) in Colby 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 Colby?
The first hard freeze (28°F) in Colby typically arrives around Oct 18, per NOAA 1991–2020 climate normals — the point tender summer crops finish. Lighter frosts run ahead of it, near Oct 4, so the watching starts about Sep 18 — about 181 days after the spring freeze cleared.
How long is the growing season in Colby?
Measured between 28°F hard freezes, Colby sees about 181 frost-free days — roughly Apr 20 through Oct 18, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer May 11 to Oct 4, about 146 days.
Is the soil safe to grow vegetables in Colby?
The federal record around Colby is a meaningful one — 162 documented sites, mostly Underground Storage Tanks entries (63), the nearest Underground Storage Tanks record about 0.2 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 Colby?
From about Sep 18 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 18 (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 18. Hardy greens and roots shrug off light frost and sweeten after it — leave them in.
Everything above is measured at Colby's scale — its 6a band and its 181-day season. Your yard writes its own version of Colby'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 Colby’s own scale
7 of the readings below were taken at Colby's own scale — its own ~181-day season between 28°F freezes, the 2,353 acres it covers and 162 documented sites around it; 4 are borrowed from a wider read, named and linked below.
Measured here
- Colby's own USDA hardiness band, zones 6aUSDA PHZM 2023
- Colby's own 28°F hard-freeze dates, about Apr 20 and Oct 18 and the ~181-day span between themNOAA 1991–2020 Climate Normals
- 162 documented contamination sites on the federal record near Colby, the closest Underground Storage Tanks record about 0.2 miles out from the town centreFederal environmental registers
- Colby's boundary and the 2,353 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 6a and a ~181-day seasonGrowable Ground crop-matching engine
- The ecoregion at Colby's own centroid, the High PlainsUS EPA Level III Ecoregions
- Lanternfly survey cells around Colby checked, none carrying a detectionlydemapr (De Bona & Helmus), 10 km survey lattice
Inherited from a wider read
- Soil character — no town-scale survey exists, so Colby's 2,353 acres read through its county's SSURGO summaryfrom Thomas County
- Growing-degree days and winter chill — measured county-wide only, so the county page carries themfrom Thomas County
- The growing challenges every Kansas grower plans around — written at state scale, so they stay on the state guidefrom Kansas
- Butterfly and beetle records, and the farmland pesticide estimate — all published county-widefrom Thomas County
What this page can’t tell you
- The soil pH, drainage, sun hours, and frost pockets on any one lot among Colby's 2,353 acreswhy one lot differs from the next →
- Which side of Colby you're on — a low spot frosts first and a south wall warms early, and one normal is being asked to speak for all 2,353 acresreading your own microclimate →
- How close that record sits to YOUR lot — the closest Underground Storage Tanks record about 0.2 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 Colby-wide figureread your own land →
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