Dauphin Island, Alabama, sits in USDA hardiness zone 9b — 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 — okra, collard greens, fig, and pecan — with any one site's soil, sun, and drainage making the final cut.
Even in Dauphin Island, 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 Dauphin Island 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 Dauphin Island — soil, climate, flood, and parcel records. How we handle your address.
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Dauphin Island — the short answer
Dauphin Island, Alabama: USDA zone 9b, about 297 days between hard freezes, across 4K acres of town.
- USDA zone
- 9b
- USDA PHZM 2023
- Last hard freeze (28°F)
- Feb 9
- Mobile County normal — NOAA 1991–2020, nearest to this town
- First hard freeze (28°F)
- Dec 3
- Mobile County normal — NOAA 1991–2020, nearest to this town
- Days between freezes
- ~297
- Mobile County normal — NOAA 1991–2020, nearest to this town
- Town area
- 4K acres
- US Census TIGER/Line 2025
Every figure names the dataset it came from. No 30-year normal resolves at this town’s own centroid, so the hard-freeze dates are Mobile County’s — the closest measured record, labelled as such rather than passed off as local.
Hardiness Zone Range
Zone 9b is Dauphin Island's average, not your lot's — a low corner or a tree line moves it. Against Dauphin Island's 297-day season, see what your own ground reads.
Soil varies lot by lot — soil types explained.
What this means for growing in Dauphin Island
Each reading below is measured for Dauphin Island itself — here is what it means for a garden here, and the move an experienced grower makes about it.
Season length
From county recordsDauphin Island runs about 297 days between hard freezes (read from Mobile County, the closest normal to Dauphin Island) — close to year-round growing.
Frost is rarely the limit here; winter plantings are as real as summer ones, and the harder question is which crops shrug off the summer heat.
Grow cool-season crops through the mild winter, and choose heat-tolerant varieties for the summer beds.
NOAA 1991–2020 Climate Normals
Winter hardiness
MeasuredDauphin Island sits in USDA hardiness zone 9b.
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 Dauphin Island is in
Dauphin Island sits in the Southern Coastal Plain — EPA Level III, inside the wider Eastern Temperate Forests. That is read at Dauphin Island's own centroid, and it is not what its county reads: Mobile County is mostly Southeastern Plains. The wider page above you is answering a different question about different ground.
What Grows in Dauphin Island
Plants matched to Dauphin Island's USDA zones 9b, ordered by how much hardiness margin each has here — the ones with room to spare at both ends of this town's band lead. Each links to its full growing profile.
Is it too late to plant in Dauphin Island?
Usually not — gardeners here simply switch what goes in the ground as the season moves. Cool-season crops can go in from around Jan 12; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near Feb 9 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Dec 3 — long-season crops need about 90 days of runway, quick greens only 30. With almost year-round growing weather, timing is about heat and rainfall more than frost — some bench is always in play.
What's on the federal record near Dauphin Island
Closest first, within ~10 miles of Dauphin Island. Listing isn't leaking, and distance isn't exposure.
- Well UU 2 301514088071701 Mobile County AlNitrate · 3.0 mi
- Well UU 73 Mobile Cnty ALNitrate · 3.5 mi
- CIRCLE K #8242Underground Storage Tanks · 3.5 mi
- ISLAND CHEVRON & GRILLUnderground Storage Tanks · 3.5 mi
- Well UU 54 Mobile Cnty ALNitrate · 3.5 mi
- MARINE RESOURCES DIV AL DEPT CONSERVUnderground Storage Tanks · 3.8 mi
- FDA GULF COAST SEAFOOD LABBrownfields · 3.9 mi
- DAUPHIN ISLAND WATER & SEWERPFAS · 4.1 mi
- W&T OFFSHORE, INC.Toxics Release Inventory · 5.2 mi
- NORTHWEST GULF FIELDToxics Release Inventory · 5.2 mi
- US COAST GUARD STATION DAUPHIN ISLANDBrownfields · 5.4 mi
- W & T OFFSHORE, INC.Toxics Release Inventory · 7.6 mi
6 more sites are on the record inside the same radius. See them on the map
Measured from Dauphin Island'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 Dauphin Island.
Total Sites
34
within ~10 miles of Dauphin Island
Risk Level
Low
Highest-severity
8 Toxics Release Inventory facilities
Sources Checked
within ~10 miles of Dauphin Island
Severity Distribution
within ~10 miles of Dauphin Island
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around Dauphin Island, two things run higher than the national average within ~10 miles of Dauphin Island — Toxics Release Inventory (8 sites) and Nitrate (12 sites). 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.
Nitrate: Nitrate contamination primarily comes from agricultural fertilizer runoff and failing septic systems.
Check prevailing wind direction — downwind parcels face higher exposure than upwind or crosswind locations.
Test well water for nitrate if you rely on a private well for irrigation (EPA standard: 10 mg/L).
Check your specific parcel in Dauphin Island
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 Dauphin Island average
Your land is one point inside Dauphin Island
Everything above resolves to Dauphin Island as a whole — one PHZM band, read across 4K acres, with hard-freeze dates borrowed from Mobile County’s record because no 30-year normal resolves at this town’s own centroid. 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 Dauphin Island Average
Dauphin Island Average
- ●USDA Zones 9b, averaged across Dauphin Island
- ●One soil character for all of Dauphin Island
- ●Frost dates read at Dauphin Island's scale: Feb 9 to Dec 3
YOUR Parcel
- ✓Your exact zone, not Dauphin Island's 9b
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your specific parcel in Dauphin Island
Pull a site-specific report for your exact address in Dauphin Island, Alabama — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Dauphin Island averages can't show:
We read public map data around Dauphin Island — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Dauphin Island average
How we know this about Dauphin Island
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 Mobile County’s record, because none resolves here; 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 Dauphin Island
When does frost risk typically end in Dauphin Island?
The last hard freeze (28°F) in Dauphin Island typically lands around Feb 9, 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 Mar 2.
When is the first frost in Dauphin Island?
The first hard freeze (28°F) in Dauphin Island typically arrives around Dec 3, per NOAA 1991–2020 climate normals — the point tender summer crops finish. Lighter frosts run ahead of it, near Nov 19, so the watching starts about Nov 3 — about 297 days after the spring freeze cleared.
How long is the growing season in Dauphin Island?
Measured between 28°F hard freezes, Dauphin Island sees about 297 frost-free days — roughly Feb 9 through Dec 3, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer Mar 2 to Nov 19, about 262 days.
Is the soil safe to grow vegetables in Dauphin Island?
The federal record around Dauphin Island is light — 34 documented sites across the 9 federal source types we checked, mostly Nitrate entries (12), the nearest Nitrate record about 3.0 miles out — and proximity to a documented site is information, not a diagnosis of any one yard. Growing food here starts from a strong position; a soil test before new food beds settles any site-specific question.
How do I protect my plants from frost in Dauphin Island?
From about Nov 3 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 Dec 3 (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 Dec 3. Hardy greens and roots shrug off light frost and sweeten after it — leave them in.
Everything above is measured at Dauphin Island's scale — its 9b band and its 297-day season. Your yard writes its own version of Dauphin Island'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 Dauphin Island’s own scale
4 of the readings below were taken at Dauphin Island's own scale — the 4,004 acres it covers and 34 documented sites around it; 6 are borrowed from a wider read, named and linked below.
Measured here
- Dauphin Island's own USDA hardiness band, zones 9bUSDA PHZM 2023
- 34 documented contamination sites on the federal record near Dauphin Island, the closest Nitrate record about 3.0 miles out from the town centreFederal environmental registers
- Dauphin Island's boundary and the 4,004 acres inside itUS Census TIGER/Line 2025
- Dauphin Island sits in the Southern Coastal Plain — not the ecoregion its county mostly readsUS EPA Level III Ecoregions
Inherited from a wider read
- The 28°F hard-freeze dates — Dauphin Island has no normal of its own, so its county's is the closest measured readfrom Mobile County
- Soil character — no town-scale survey exists, so Dauphin Island's 4,004 acres read through its county's SSURGO summaryfrom Mobile County
- The candidate plant list — Alabama's curated set, filtered to this zone band and re-ordered by how much margin each has herefrom Alabama
- Growing-degree days and winter chill — measured county-wide only, so the county page carries themfrom Mobile County
- The growing challenges every Alabama grower plans around — written at state scale, so they stay on the state guidefrom Alabama
- Butterfly and beetle records, and the farmland pesticide estimate — all published county-widefrom Mobile County
What this page can’t tell you
- The soil pH, drainage, sun hours, and frost pockets on any one lot among Dauphin Island's 4,004 acreswhy one lot differs from the next →
- Which side of Dauphin Island you're on — a low spot frosts first and a south wall warms early, and one normal is being asked to speak for all 4,004 acresreading your own microclimate →
- How close that record sits to YOUR lot — the closest Nitrate record about 3.0 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 Dauphin Island-wide figureread your own land →
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