USDA zone 9b in Alabama
USDA plant hardiness zone 9b covers 1 location across Alabama (average annual extreme minimum 25 to 30 °F): Dauphin Island, AL. Average last spring frost across this group ranges January 31 and growing seasons run 340 days — even within one state, because hardiness sets winter survival, not planting dates. The table below gives every Alabama location's own frost dates; the printable planting calendar uses Dauphin Island, this group's median-season location.
- USDA zone
- 9b25 to 30 °F
- Last frost range
- Jan 31avg, 32°F
- First frost range
- Jan 6avg, 32°F
- Growing season range
- 340days
Locations in this group
Every location below shares this zone and a nearby weather station, but keeps its own frost dates — find your town for its own numbers, or use the ZIP planner on the home page for an instant personalized answer.
| Location | Also covers | Nearest station | Last frost | First frost | Season (days) |
|---|---|---|---|---|---|
| Dauphin Island * | — | Dauphin Is #2 | Jan 31 | Jan 6 | 340 |
* Dauphin Island is this group's median-season location — the calendar below is computed from its data.
Data: NOAA NCEI U.S. Climate Normals 1991–2020 (public domain) and USDA Plant Hardiness Zone Map 2023. Planting windows synthesized from U.S. Cooperative Extension guides.
Planting calendar (Dauphin Island, representative)
Computed from Dauphin Island's average frost dates — the median-season location in this Alabamazone 9b group. hatched = start seeds indoors, solid green = plant out, teal = a fall sowing, and the terracotta dot marks the estimated first harvest. Ranges are extension-guide planning guidance, not guarantees — your own location's dates may run a week or two earlier or later (see the table above).
- Start indoors
- Plant out
- Fall sowing
- First harvest
| Crop | Frost tolerance | Start indoors | Plant out | First harvest | Fall planting | Season fit |
|---|---|---|---|---|---|---|
| Tomato | Tender | Jan 1 | Feb 7 – Feb 14 | Apr 8 – Apr 28 | — | matures comfortably |
| Pepper | Very tender | Jan 1 | Feb 14 – Feb 21 | Apr 15 – May 15 | — | matures comfortably |
| Cucumber | Tender | Jan 3 – Jan 10 | Feb 7 – Feb 14 | Mar 29 – Apr 18 | — | matures comfortably |
| Summer squash / zucchini | Tender | — | Feb 7 – Feb 14 | Mar 24 – Apr 8 | — | matures comfortably |
| Bush bean | Tender | — | Feb 7 – Feb 14 | Mar 29 – Apr 8 | — | matures comfortably |
| Sweet corn | Tender | — | Jan 31 – Feb 14 | Apr 1 – May 1 | — | matures comfortably |
| Basil | Very tender | Jan 1 – Jan 3 | Feb 7 – Feb 14 | Mar 9 – Mar 24 | — | matures comfortably |
| Lettuce | Half-hardy | Jan 1 – Jan 3 | Jan 3 – Jan 17 | Feb 17 – Mar 4 | — | matures comfortably |
| Pea | Hardy | — | Jan 1 – Jan 3 | Feb 25 – Mar 12 | — | matures comfortably |
| Spinach | Hardy | — | Jan 1 – Jan 3 | Feb 10 – Feb 20 | — | matures comfortably |
| Carrot | Half-hardy | — | Jan 10 – Jan 17 | Mar 11 – Mar 31 | — | matures comfortably |
| Broccoli | Half-hardy | Jan 1 | Jan 3 – Jan 17 | Feb 27 – Mar 19 | — | matures comfortably |
Which crops fit this growing season
Using Dauphin Island's own 340-day growing season (32°F, NOAA 1991–2020 median) against each crop's real days-to-maturity range: 12 of 12 crops mature here with comfortable margin. A different location in the table above with a longer or shorter season will get a different mix — the ZIP planner on the home page gives your own.
Frost & freeze dates (Dauphin Island)
From NOAA's 1991–2020 Climate Normals at station USC00012172. The median (p50) is the average date; the 90%-safe column is the date the freeze has passed in about 9 years out of 10 — the conservative date to plant after or harvest before.
| Threshold | Last spring — avg | Last spring — 90%-safe | First fall — avg | First fall — 90%-safe | Season (days) |
|---|---|---|---|---|---|
| 36°F | Feb 11 | Mar 10 | Dec 28 | Jan 21 | 313 |
| 32°F (freeze) | Jan 31 | Feb 27 | Jan 6 | Feb 2 | 340 |
| 28°F | Jan 21 | Feb 11 | Jan 13 | Feb 4 | 365 |
| 24°F | Jan 21 | Feb 7 | Jan 17 | Feb 6 | 365 |
Growing degree days
Growing degree days (GDD) accumulate warmth above a base temperature over the year — a better predictor of crop development than the calendar alone. This group's median GDD (base 50°F) across all 1 locations is 7,183; Dauphin Island's own reading is shown below.
| Model | °F·days | Used for |
|---|---|---|
| Base 50°F (warm-season) | 7,183 | standard warm-season base (tomato, corn, beans) |
| Base 40°F (cool-season) | 10,699 | cool-season crops (brassicas, greens) |
Hardiness zone 9b in Alabama
Zone 9b means an average annual extreme minimum winter temperature of about 25 to 30 °F on the USDA's 2023 map — the number that tells you which perennials, shrubs, and trees reliably survive an average winter here. It does not set your planting dates, which come from the frost calendar above. Alabama spans 5 hardiness zones in this dataset — see all Alabama locations for the full range, including zones7b, 8a, 8b, 9a.
Explore zone 9b in other states at zone 9b, or see all USDA hardiness zones.
Frequently asked questions
- What does USDA hardiness zone 9b mean in Alabama?
- Zone 9b means an average annual extreme minimum winter temperature of 25 to 30 °F — the standard USDA measure of which perennials survive winter. 1 location in Alabama fall in this zone. It does not set planting dates; see the frost calendar below for that.
- When should I plant tomatoes in Alabama's zone 9b?
- Using Dauphin Island's frost dates (this page's median-season location): start seeds indoors about Jan 1, then transplant outside about Feb 7 – Feb 14. Your own location in the table above may differ by a week or two — use the ZIP planner on the home page for your exact station's dates.
- Does every location in Alabama's zone 9b have the same frost dates?
- No — they do not all share a weather station, so frost dates vary by a week or more across the 1 locations listed (see the table above for each location's own dates).
Sources & method
Frost, freeze, growing-season, and growing-degree-day figures are NOAA NCEI U.S. Climate Normals 1991–2020, one reading per location's own nearest station (see the table above). The hardiness zone is the USDA Plant Hardiness Zone Map 2023, matched to each location's ZIP. Planting windows are computed by counting from the average last and first frost using per-crop offsets synthesized from U.S. Cooperative Extension guides — the full method and citations are on the methodology page.