Dubuque County, in Iowa, sits in USDA hardiness zone 5a — a range where zone-matched perennials and frost-aware annual timing set what succeeds.
Among the crops suited to this profile: cabbage, cranberry, lavender, and collard greens. The site-level story — soil, sun, drainage — decides the rest.
Dubuque County lies within the Driftless Area — a regional growing area with its own character.
Grounded in USDA PHZM 2023 · Growable Ground suitability scoring · NOAA 1991–2020 Climate Normals
Dubuque County holds more than one microclimate.
Soils and elevations shift across Dubuque 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 Dubuque County — soil, climate, flood, and parcel records. How we handle your address.
No card required · your full report in seconds
Dubuque County — the short answer
Dubuque County, Iowa: USDA zone 5a, about 189 days between hard freezes, across 389K acres.
- USDA zone
- 5a
- USDA PHZM 2023
- Last hard freeze (28°F)
- Apr 14
- NOAA 1991–2020 Climate Normals, 28°F
- First hard freeze (28°F)
- Oct 20
- NOAA 1991–2020 Climate Normals, 28°F
- Days between freezes
- ~189
- 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 5a is Dubuque County's average, not your lot's — a low corner or a tree line moves it. Against Dubuque County's 189-day season, see what your own ground reads.
Heat in Dubuque County
Across a year, Dubuque County accumulates about 2,469 growing degree days above 50°F, about 275 fewer than the middle Iowa county — ahead of 13 of Iowa’s 99 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 Dubuque County
Across Dubuque County, the ground is predominantly Alfisols, where Fayette, Downs, and Nordness are the most extensive named soil series. The soil is generally well drained with a silt loam surface. Topsoil pH runs about 6.2–6.5, slightly acidic. Rainfall drains through hydrologic group C soils.
Soil order
Alfisols
Drainage
Well drained
Prime farmland
13%
Hydric soils
3%
Soil still varies lot by lot — soil types explained.
How the ground varies across Dubuque County
The USDA soil survey maps 68% of Dubuque County as well drained — but another 29% drains differently: 20% moderately well drained, 3% poorly drained.
Fayette is the most extensive named soil at 28% of mapped acres, then Downs (15%) and Nordness (9%).
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 Dubuque County
Each reading below is measured for Dubuque 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 Dubuque County are well drained, in hydrologic group C — 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 Dubuque County runs about pH 6.2–6.5, 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
MeasuredDubuque County runs about 189 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
MeasuredDubuque County sits in USDA hardiness zone 5a.
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 Dubuque County is in
Dubuque County spans 2 EPA Level III ecoregions — Driftless Area (57%) and Western Corn Belt Plains (43%). Which one your land falls in changes what grows wild there and how the ground behaves, and a county-wide answer cannot tell you which.
What Grows in Dubuque County
We scored all 1,086 plants against Dubuque County's own USDA zone 5a and its own 189-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 Iowa profile.
Is it too late to plant in Dubuque County?
For most of the year, no — what changes is which crops still fit the days remaining. Cool-season crops can go in from around Mar 17; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near Apr 14 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Oct 20 — 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 Dubuque County
- Japanese beetle5 documented records
- monarch butterfly149 documented records
Sighting records, so they follow observers as much as insects.
What gets applied to farmland in Dubuque County
USGS estimates 179,551 lb of Glyphosate on Dubuque County farmland in 2019, its largest by weight, ahead of Acetochlor (111,717 lb) and Atrazine (70,953 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 Dubuque County — and how to grow with it.
We checked the federal record across Dubuque County — 659 documented sites across 7 of the 9 source types we track.
The most significant on record: 3 Superfund sites. Sites tracked in EPA's Superfund program — from assessment-stage CERCLIS entries to confirmed National Priorities List cleanup sites.
Dubuque 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 Dubuque County
Closest first, across Dubuque County. Listing isn't leaking, and distance isn't exposure.
- BERRY PLASTICSBrownfields · 1.5 mi
- FEDEX FREIGHT DBQBrownfields · 1.6 mi
- ROADWAY EXPRESS INCUnderground Storage Tanks · 1.6 mi
- MI-T-M CORPORATIONUnderground Storage Tanks · 1.6 mi
- THREE RIVERS FS COMPANYUnderground Storage Tanks · 1.7 mi
- COUNTRY STOREUnderground Storage Tanks · 1.7 mi
- CAPTIVE PLASTICSBrownfields · 1.8 mi
- CAMSO MANUFACTURING USA LTDToxics Release Inventory · 1.9 mi
- MCDERMOTT EXCAVATINGUnderground Storage Tanks · 1.9 mi
- SWISS VALLEY PARKUnderground Storage Tanks · 1.9 mi
- NORTHEAST IOWA TECHNICAL INSTITUTEUnderground Storage Tanks · 1.9 mi
- CAMSO MANUFACTURING LTDBrownfields · 1.9 mi
6 more sites are on the record inside the same radius. See them on the map
Measured from Dubuque 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 Dubuque County.
Sources Checked
across Dubuque County
Severity Distribution
across Dubuque County
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around Dubuque County, Toxics Release Inventory runs higher than the national average — 43 sites across Dubuque County. 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 Dubuque 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 Dubuque County average
Your land is one point inside Dubuque County
Everything above resolves to Dubuque 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 Dubuque County Average
Dubuque County Average
- ●USDA Zones 5a, averaged across Dubuque County
- ●One soil character for all of Dubuque County
- ●Frost dates read at Dubuque County's scale: Apr 14 to Oct 20
YOUR Parcel
- ✓Your exact zone, not Dubuque County's 5a
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your parcel in Dubuque County
Pull a site-specific report for your exact address in Dubuque County, Iowa — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Dubuque County averages can't show:
We read public map data around Dubuque County — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Dubuque County average
How we know this about Dubuque 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 Dubuque County carries no record of its own, the figure is inherited and labelled — the resolution ledger below names each.
Common questions about Dubuque County
When does frost risk typically end in Dubuque County?
The last hard freeze (28°F) in Dubuque County typically lands around Apr 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 May 5.
How long is the growing season in Dubuque County?
Measured between 28°F hard freezes, Dubuque County sees about 189 frost-free days — roughly Apr 14 through Oct 20, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer May 5 to Oct 6, about 154 days.
Is the soil safe to grow vegetables in Dubuque County?
The federal record around Dubuque County runs heavier than most — 659 documented sites, mostly Underground Storage Tanks entries (346), the nearest Brownfields record about 1.5 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.
Everything above is measured at Dubuque County's scale — its 5a band and its 189-day season. Your yard writes its own version of Dubuque 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 Iowa's frost window, season length, and soil profile against the plant's real requirements.
What this page reads at Dubuque County’s own scale
9 of the readings below were taken at Dubuque County's own scale — its own ~189-day span between 28°F freezes, the 3 most extensive soil series mapped here and 659 documented sites inside its boundary; one is borrowed from a wider read, named and linked below.
Measured here
- Dubuque County's own USDA hardiness band, zones 5aUSDA PHZM 2023
- Dubuque County's own 28°F hard-freeze dates and its ~189-day span between themNOAA 1991–2020 Climate Normals
- The soil order, drainage, surface pH, and the 3 most extensive named soil series mapped in Dubuque CountyUSDA NRCS SSURGO
- 659 documented contamination sites inside the county boundary, distance-sorted from its center — the closest Brownfields record about 1.5 miles outFederal environmental registers
- Dubuque County's boundary and the 389,311 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 5a and a ~189-day seasonGrowable Ground crop-matching engine
- The 2 ecoregions Dubuque County spans, Driftless Area the largestUS EPA Level III Ecoregions
- Open occurrence records documented in Dubuque County for 2 tracked speciesGBIF derived datasets (CC0 / CC BY 4.0)
- Which agricultural compounds go onto Dubuque County farmland, and roughly how muchUSGS NAWQA EPest county estimates
Inherited from a wider read
- The growing challenges every Iowa grower plans around — written at state scale, so they stay on the state guidefrom Iowa
What this page can’t tell you
- How the season shifts across Dubuque County — the ~189 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 Dubuque County's 389,311 acreswhy one lot differs from the next →
- Which of those 659 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 Dubuque Countyread your own land →