Data: 2023 USDA zones (PRISM/OSU) · NOAA 1991–2020 normals · updated

Planting zone for 29482 — Sullivans Island, SC

ZIP code 29482 (Sullivans Island, Charleston County) is in USDA zone 9a: the coldest winter night averages 20 to 25 °F. The median last spring frost is March 13 and the first fall frost November 30.

Where ZIP 29482 is

Outlined: the ZIP code area · tap the map for the zone at any spot · scroll or pinch to zoom

Not the official USDA Plant Hardiness Zone Map. Zones come from the 2023 USDA hardiness-zone data by the PRISM Group, Oregon State University; we re-mapped and recolored them. The official map is at planthardiness.ars.usda.gov.

Zone9a20 to 25 °F
Coldest night−6.7 to −3.9 °C
Last frostMar 13
First frostNov 30
2012 zone8b

Was 8b on the 2012 map — half a zone warmer now. The zone is the one at the center of the ZIP code; hilly ZIPs can span two zones. What zone 9a means →

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for Sullivans Island, SC…

Forecast data: National Weather Service (api.weather.gov), public domain. This is not a warning service — for official frost and freeze warnings see weather.gov.

Frost dates in Sullivans Island, SC

JanFebMarAprMayJunJulAugSepOctNovDec
Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free
Last spring frostMarch 13median — 50% chance of a later frost
Safe for tender plantsMarch 30only 10% chance of frost after
First fall frostNovember 30median — 10% chance by Nov 11
Growing season262 daysfrost-free, median

A hard freeze (28 °F) usually ends around March 1 and returns around December 16.

From the NOAA station Sullivans Is, SC — 2 miles away, elevation 7 ft. NOAA NCEI U.S. Climate Normals 1991–2020, 32 °F threshold. Low spots and valleys can freeze later in spring than the station.

When to plant vegetables in 29482

JanFebMarAprMayJunJulAugSepOctNovDec
PeasSow outdoors · Jan 30 – Feb 13
SpinachSow outdoors · Jan 30 – Feb 20
Broccoli, cabbageStart indoors · Jan 2 – Jan 16
Broccoli, cabbageTransplant · Feb 20 – Mar 6
Onion setsPlant outdoors · Feb 13 – Feb 27
PotatoesPlant outdoors · Feb 20 – Mar 6
LettuceSow outdoors · Feb 13 – Feb 27
Carrots, beetsSow outdoors · Feb 20 – Mar 6
TomatoesStart indoors · Jan 16 – Jan 30
TomatoesTransplant · Mar 20 – Apr 3
Peppers, eggplantStart indoors · Jan 2 – Jan 16
Peppers, eggplantTransplant · Mar 27 – Apr 10
BeansSow outdoors · Mar 20 – Apr 3
Sweet cornSow outdoors · Mar 20 – Apr 3
Cucumbers, squashSow outdoors · Mar 20 – Apr 3
Fall lettuce, spinachSow outdoors · Oct 5 – Oct 19
GarlicPlant cloves · Nov 16 – Dec 21
Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (Mar 13) and first fall frost (Nov 30) with the rules of thumb U.S. extension services publish. Cool-season crops take a light frost; warm-season crops do best once the soil is above about 60 °F.

When spring arrived in 2026

In 2026, spring leaf-out near 29482 came on Feb 7 — 8 days later than the 1991–2020 average (Jan 30).

JanFebMarAprMayJun

The Spring Index marks the day when accumulated warmth is enough for lilac and honeysuckle to leaf out — a widely used signal that the growing season has started. Source: USA National Phenology Network, www.usanpn.org — Spring Indices, first leaf, 2026 (data as of 2026-09-08) and 30-year average 1991–2020 (CC BY 4.0).

Soil in Sullivans Island, SC

The soil mapped at the center of ZIP 29482 is Bohicket — silty clay loam, very poorly drained.

TextureSilty clay loamholds water and nutrients; slow to drain and warm up
pH4.7strongly acidic; most vegetables like 6.0–7.0
DrainageVery poorly drainedconsider raised beds
Organic matter0.25%low — add compost
Hydrologic groupC/Dslow when drained; wet otherwise
Farmland classNot prime farmlandUSDA classification

Map unit: Tidal marsh, soft.

Soil Survey Staff, Natural Resources Conservation Service, USDA. Soil Survey Geographic (SSURGO) Database, via Soil Data Access, accessed 2026-10-29. The soil at the center point of ZIP 29482; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Sullivans Island, SC

Summer high91 °Faverage high, July
Winter low37 °Faverage low, January
Hot days55days a year at 90 °F or more
Freezing nights18nights a year at 32 °F or less
Growing degree days6,058base 50 °F — the season’s usable heat
Longest day14 h 19 mindaylight on June 21
Shortest day9 h 59 mindaylight on December 21
Onions to growIntermediateday-neutral types bulb best; long-day varieties may not bulb fully
Precipitation51.6 inper year, rain and melted snow

Average high and low, by month

30°40°50°60°70°80°90°100°32 °FJanuary: average high 59 °F, low 37 °F 59°37° JanFebruary: average high 61 °F, low 39 °F 61°39° FebMarch: average high 67 °F, low 45 °F 67°45° MarApril: average high 75 °F, low 54 °F 75°54° AprMay: average high 82 °F, low 63 °F 82°63° MayJune: average high 88 °F, low 70 °F 88°70° JunJuly: average high 91 °F, low 73 °F 91°73° JulAugust: average high 90 °F, low 72 °F 90°72° AugSeptember: average high 86 °F, low 68 °F 86°68° SepOctober: average high 78 °F, low 58 °F 78°58° OctNovember: average high 69 °F, low 47 °F 69°47° NovDecember: average high 62 °F, low 40 °F 62°40° Dec

Precipitation by month inches

0″2″4″6″January: 3.81 in precipitation 3.8 JanFebruary: 3.30 in precipitation 3.3 FebMarch: 3.49 in precipitation 3.5 MarApril: 3.59 in precipitation 3.6 AprMay: 3.33 in precipitation 3.3 MayJune: 5.36 in precipitation 5.4 JunJuly: 5.97 in precipitation 6.0 JulAugust: 6.72 in precipitation 6.7 AugSeptember: 5.47 in precipitation 5.5 SepOctober: 3.94 in precipitation 3.9 OctNovember: 3.00 in precipitation 3.0 NovDecember: 3.62 in precipitation 3.6 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Sullivans Is, SC (2 mi away); precipitation: Sullivans Is, SC (2 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

All 8 nearest ZIP codes share zone 9a.

294659a
Mount Pleasant, SC · 2 mi
294649a
Mount Pleasant, SC · 4 mi
294139a
Charleston, SC · 6 mi
294169a
Charleston, SC · 6 mi
294179a
Charleston, SC · 6 mi
294229a
Charleston, SC · 6 mi
294239a
Charleston, SC · 6 mi
294029a
Charleston, SC · 6 mi

South Carolina planting zones →

Questions about 29482

What planting zone is ZIP code 29482?

ZIP code 29482 (Sullivans Island, SC) is in USDA hardiness zone 9a on the 2023 map: the coldest night of an average winter reaches 20 to 25 °F (−6.7 to −3.9 °C).

When is the last frost in Sullivans Island, SC?

The median last spring frost (32 °F) near 29482 is March 13; after March 30 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Sullivans Is station.

When is the first frost in Sullivans Island, SC?

The median first fall frost near 29482 is November 30, giving a median frost-free growing season of 262 days.

When should I plant tomatoes in 29482?

Start tomato seeds indoors around Jan 16 – Jan 30 and set transplants outside around Mar 20 – Apr 3, one to three weeks after the median last frost.

How much rain and snow does 29482 get?

About 51.6 inches of precipitation a year (NOAA 1991–2020 normals, Sullivans Is station).

How hot do summers get in Sullivans Island, SC?

The average high peaks at 91 °F in July, with about 55 days a year at 90 °F or more.

What kind of soil does 29482 have?

The USDA soil survey maps Bohicket at the center of ZIP 29482: silty clay loam, very poorly drained, pH about 4.7 (strongly acidic).

Did spring come early in Sullivans Island, SC in 2026?

Spring leaf-out near 29482 came on Feb 7 in 2026, 8 days later than the 1991–2020 average (Jan 30), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Sullivans Island, SC?

Intermediate onions: the longest day near 29482 is 14 h 19 min, so day-neutral types bulb best; long-day varieties may not bulb fully.

Did the zone for 29482 change?

Yes. The 2012 USDA map put 29482 in zone 8b; the 2023 map puts it in zone 9a. The newer map uses 1991–2020 data and more weather stations.