USDA zone 9b in South Carolina
USDA plant hardiness zone 9b covers 1 location across South Carolina (average annual extreme minimum 25 to 30 °F): Hilton Head Island, SC. Average last spring frost across this group ranges February 28 and growing seasons run 279 days — even within one state, because hardiness sets winter survival, not planting dates. The table below gives every South Carolina location's own frost dates; the printable planting calendar uses Hilton Head Island, this group's median-season location.
- USDA zone
- 9b25 to 30 °F
- Last frost range
- Feb 28avg, 32°F
- First frost range
- Dec 3avg, 32°F
- Growing season range
- 279days
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) |
|---|---|---|---|---|---|
| Hilton Head Island * | Fripp Island | Beaufort Mcas | Feb 28 | Dec 3 | 279 |
* Hilton Head 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 (Hilton Head Island, representative)
Computed from Hilton Head Island's average frost dates — the median-season location in this South Carolinazone 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 3 – Jan 17 | Mar 7 – Mar 14 | May 6 – May 26 | — | matures comfortably |
| Pepper | Very tender | Jan 1 – Jan 3 | Mar 14 – Mar 21 | May 13 – Jun 12 | — | matures comfortably |
| Cucumber | Tender | Jan 31 – Feb 7 | Mar 7 – Mar 14 | Apr 26 – May 16 | — | matures comfortably |
| Summer squash / zucchini | Tender | — | Mar 7 – Mar 14 | Apr 21 – May 6 | — | matures comfortably |
| Bush bean | Tender | — | Mar 7 – Mar 14 | Apr 26 – May 6 | Oct 4 – Oct 14 | matures comfortably |
| Sweet corn | Tender | — | Feb 28 – Mar 14 | Apr 29 – May 29 | — | matures comfortably |
| Basil | Very tender | Jan 17 – Jan 31 | Mar 7 – Mar 14 | Apr 6 – Apr 21 | — | matures comfortably |
| Lettuce | Half-hardy | Jan 17 – Jan 31 | Jan 31 – Feb 14 | Mar 17 – Apr 1 | Sep 20 – Oct 5 | matures comfortably |
| Pea | Hardy | — | Jan 17 – Jan 31 | Mar 13 – Mar 28 | Sep 10 – Sep 25 | matures comfortably |
| Spinach | Hardy | — | Jan 17 – Jan 31 | Feb 26 – Mar 8 | Sep 30 – Oct 10 | matures comfortably |
| Carrot | Half-hardy | — | Feb 7 – Feb 14 | Apr 8 – Apr 28 | Aug 31 – Sep 20 | matures comfortably |
| Broccoli | Half-hardy | Jan 3 – Jan 17 | Jan 31 – Feb 14 | Mar 27 – Apr 16 | Sep 5 – Sep 25 | matures comfortably |
Which crops fit this growing season
Using Hilton Head Island's own 279-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 (Hilton Head Island)
From NOAA's 1991–2020 Climate Normals at station USW00093831. 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 | Mar 14 | Mar 31 | Nov 18 | Dec 8 | 249 |
| 32°F (freeze) | Feb 28 | Mar 21 | Dec 3 | Jan 1 | 279 |
| 28°F | Feb 8 | Mar 8 | Dec 27 | Jan 28 | 312 |
| 24°F | Jan 27 | Feb 27 | Jan 7 | Feb 7 | 348 |
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 6,582; Hilton Head Island's own reading is shown below.
| Model | °F·days | Used for |
|---|---|---|
| Base 50°F (warm-season) | 6,582 | standard warm-season base (tomato, corn, beans) |
| Base 40°F (cool-season) | 9,993 | cool-season crops (brassicas, greens) |
Hardiness zone 9b in South Carolina
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. South Carolina spans 5 hardiness zones in this dataset — see all South Carolina 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 South Carolina?
- 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 South Carolina fall in this zone. It does not set planting dates; see the frost calendar below for that.
- When should I plant tomatoes in South Carolina's zone 9b?
- Using Hilton Head Island's frost dates (this page's median-season location): start seeds indoors about Jan 3 – Jan 17, then transplant outside about Mar 7 – Mar 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 South Carolina'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.