Sullivan's Island, South Carolina climate: Normal weather by month, frost dates and records
Sullivan's Island's normal year runs from 37°F January nights to 91°F July afternoons, with 51.6 inches of precipitation a year. (NOAA 1991-2020 normals)
In metric: a yearly mean of 18.6°C, January lows of 3°C, July highs of 33°C, 1,311 mm of precipitation a year.
- NOAA stationSullivans Island
- Station IDUSC00388405
- Location32.76°N 79.86°W
- Elevation5 ft (2 m)
- From the center2 miles
- Population1,948
On October 14, the normal high in Sullivan's Island is 79°F and the normal low 58°F.
Normals describe a typical year at the station, not a forecast. The National Weather Service forecast for Sullivan's Island.
- Jan 59° 37°
- Feb 61° 39°
- Mar 67° 45°
- Apr 75° 54°
- May 82° 63°
- Jun 88° 70°
- Jul 91° 73°
- Aug 90° 72°
- Sep 86° 68°
- Oct 78° 58°
- Nov 69° 47°
- Dec 62° 40°
Each month: normal high (large) and low, °F. Fill: the month's normal mean, colder blue to hotter red.
What is the weather like in Sullivan's Island each month?
July is the warmest month, with normal highs of 91°F; January the coldest, with normal lows of 37°F. The most precipitation falls in August (6.72 in), the least in November (3.00 in).
| Month | High | Low | Mean | Precip. | Wet days | 90°F days | Freezing nights | Daylight |
|---|---|---|---|---|---|---|---|---|
| January | 59°F | 37°F | 47.8°F | 3.81 | – | <1 | 8 | 10 h 10 min |
| February | 61°F | 39°F | 50.2°F | 3.30 | – | <1 | 4 | 11 h |
| March | 67°F | 45°F | 55.9°F | 3.49 | – | <1 | 1 | 12 h |
| April | 75°F | 54°F | 64.1°F | 3.59 | – | <1 | <1 | 13 h |
| May | 82°F | 63°F | 72.7°F | 3.33 | – | 2 | <1 | 13 h 50 min |
| June | 88°F | 70°F | 78.9°F | 5.36 | – | 10 | <1 | 14 h 20 min |
| July | 91°F | 73°F | 82.0°F | 5.97 | – | 19 | <1 | 14 h 10 min |
| August | 90°F | 72°F | 81.0°F | 6.72 | – | 16 | <1 | 13 h 20 min |
| September | 86°F | 68°F | 76.8°F | 5.47 | – | 6 | <1 | 12 h 30 min |
| October | 78°F | 58°F | 67.9°F | 3.94 | – | 1 | <1 | 11 h 30 min |
| November | 69°F | 47°F | 58.1°F | 3.00 | – | <1 | 1 | 10 h 30 min |
| December | 62°F | 40°F | 51.0°F | 3.62 | – | <1 | 4 | 10 h |
| Year (annual) | 76°F | 55°F | 65.5°F | 51.60 | – | 55 | 18 |
The same normals in °C and millimetres
| Month | High | Low | Mean | Precip. |
|---|---|---|---|---|
| January | 15°C | 3°C | 8.8°C | 97 mm |
| February | 16°C | 4°C | 10.1°C | 84 mm |
| March | 19°C | 7°C | 13.3°C | 89 mm |
| April | 24°C | 12°C | 17.8°C | 91 mm |
| May | 28°C | 17°C | 22.6°C | 85 mm |
| June | 31°C | 21°C | 26.1°C | 136 mm |
| July | 33°C | 23°C | 27.8°C | 152 mm |
| August | 32°C | 22°C | 27.2°C | 171 mm |
| September | 30°C | 20°C | 24.9°C | 139 mm |
| October | 26°C | 14°C | 19.9°C | 100 mm |
| November | 21°C | 8°C | 14.5°C | 76 mm |
| December | 17°C | 4°C | 10.6°C | 92 mm |
Source: NOAA NCEI 1991-2020 monthly normals, station USC00388405; annual normals. Wet days: 0.01 inch or more; 90°F days and freezing nights: NOAA's day counts. Daylight: sunrise to sunset on the 15th, computed from the latitude.
When is the best weather to visit Sullivan's Island?
Normal highs sit between 65°F and 85°F in March, April, May, October and November.
That is a measurement, not a recommendation: it counts the months whose normal afternoon high sits between 65°F and 85°F, where a light layer is enough by day.
Source: NOAA NCEI 1991-2020 monthly normals, station USC00388405.
When is the last frost in Sullivan's Island?
In Sullivan's Island, the last spring frost (32°F) comes after March 13 in half of years and after March 30 in one year in ten; the first autumn frost comes before November 30 in half of years and before November 11 in one year in ten.
Frost-free in half of yearsFrost in 1 to 9 years out of 10Frost most years
- Last spring frost, half of years after
- March 131 year in 10 after March 30; 9 in 10 after February 19
- First autumn frost, half of years before
- November 301 year in 10 before November 11; 9 in 10 before December 24
NOAA puts the median frost-free season at 262 days, and the season without a hard freeze (28°F) at 288 days.
A hard freeze (28°F) comes after March 1 in half of springs and before December 16 in half of autumns.
The USDA's 2023 Plant Hardiness Zone Map puts Sullivan's Island in zone 9a in ZIP code 29482.
Frost dates for every NOAA station in South Carolina · Frost dates by ZIP code
Source: NOAA NCEI 1991-2020 annual normals (frost probabilities), station USC00388405; USDA 2023 Plant Hardiness Zone Map, ZIP listings: PRISM Group, Oregon State University, https://prism.oregonstate.edu, accessed October 8, 2026. A 10% date means one year in ten has a frost after it in spring or before it in autumn.
How hot and how cold does it get in Sullivan's Island?
In a normal year in Sullivan's Island, 55 days a year reach 90°F (1 of them 100°F or more) and 18 nights fall to 32°F or colder.
- Days at 90°F or more
- 55a normal year
- Days at 100°F or more
- 1a normal year
- Nights at 32°F or colder
- 18a normal year
- Days that stay below freezing
- fewer than 1high of 32°F or less
Source: NOAA NCEI 1991-2020 annual normals, station USC00388405.
How sunny is Sullivan's Island?
Over a year 80% of the sunlight that would reach the ground under clear skies gets through the clouds in the area around Sullivan's Island, 4.7 kWh per square metre a day. May is the sunniest month (85%) and February the cloudiest (73%).
| Month | Share of clear-sky sunshine | Sunshine, kWh/m² a day |
|---|---|---|
| January | 74% | 2.8 |
| February | 73% | 3.5 |
| March | 76% | 4.6 |
| April | 84% | 6.0 |
| May | 85% | 6.5 |
| June | 84% | 6.5 |
| July | 84% | 6.3 |
| August | 82% | 5.7 |
| September | 79% | 4.8 |
| October | 81% | 4.1 |
| November | 78% | 3.1 |
| December | 73% | 2.5 |
Source: NASA POWER solar climatology, 2001-2020 (CERES SYN1deg). Satellite-based, for the 1-degree cell (about 100 km across) around the station, so it describes the area rather than the airport.
How much heating and cooling does Sullivan's Island need?
A normal year in Sullivan's Island brings 2,051 heating degree days, 62% fewer than the median U.S. place (5,373), and 2,279 cooling degree days, 2.5 times the median (908). Three months need 300 or more heating degree days, a monthly mean of about 55°F or colder. For gardens and crops, NOAA counts 6,058 growing degree days a year above 50°F.
| Month | Heating | Cooling |
|---|---|---|
| January | 532 | 0 |
| February | 415 | 0 |
| March | 289 | 7 |
| April | 91 | 66 |
| May | 9 | 248 |
| June | 1 | 418 |
| July | 0 | 529 |
| August | 0 | 496 |
| September | 1 | 355 |
| October | 47 | 137 |
| November | 229 | 22 |
| December | 438 | 3 |
| Year (annual) | 2,051 | 2,279 |
Source: NOAA NCEI 1991-2020 monthly normals, station USC00388405. A degree day is one degree of a day's mean temperature below 65°F (heating) or above it (cooling); utilities use them to estimate energy use.
Has Sullivan's Island been warmer than normal lately?
2024 averaged 67.3°F, 1.8°F above the 1991-2020 normal of 65.5°F. 2 of the 2 complete years since 2023 ran warmer than the normal.
| Year | Mean | Against normal | Precip. |
|---|---|---|---|
| 2023 | 67.8°F | +2.3°F | 58.47 |
| 2024 | 67.3°F | +1.8°F | – |
Source: observed years: ACIS, station USC00388405. A year counts only with all twelve months complete.
How does Sullivan's Island's climate compare?
Sullivan's Island is warmer than 67 of the other 72 places with their own NOAA record in South Carolina, and wetter than 48. Across the 7,247 U.S. stations with normals, its annual mean of 65.5°F is warmer than 89%.
In the Köppen classification computed from these normals, Sullivan's Island is Cfa: temperate, no dry season, hot summer. What the classes mean.
Places with the most similar year elsewhere
Measured month by month on the normal high, low and precipitation, among places of 20,000 or more people in other states:
Source: NOAA NCEI 1991-2020 normals for every station PlainClimate covers. Similarity: the root-mean-square difference of the 36 monthly figures, precipitation weighted so an inch counts like 6°F.
Which places near Sullivan's Island share this climate record?
3 places have no NOAA station with 1991-2020 normals of their own, and this station is the nearest full record. A place's own climate can differ from these figures, by several degrees where it sits much higher or lower than the station, nearer the coast, or inside a large city's heat; for the larger places the next nearest records are named with their yearly mean, so the spread around them is visible, and places of 50,000 or more have their own page with NOAA's gridded normals.
- Mount Pleasant, SCalso near: Charleston City (4 mi, 67.2°F a year); Charleston (12 mi, 66.5°F a year)95,604 people · 3 mi N
- Isle of Palms, SC4,377 people · 7 mi NE
- Awendaw, SC1,472 people · 18 mi NE
Source: Census Bureau 2024 Gazetteer (place centers) and Vintage 2024 population estimates. Distance and direction from the station to each place's center.
Questions about Sullivan's Island's climate
What is the coldest month in Sullivan's Island?
January, with a normal high of 59°F and a normal low of 37°F. The warmest is July (91°F by day, 73°F at night).
What is the rainiest month in Sullivan's Island?
August, with 6.72 in of precipitation in a normal year; the driest is November with 3.00 in.
What plant hardiness zone is Sullivan's Island in?
The USDA's 2023 map puts Sullivan's Island in zone 9a in ZIP code 29482.
How late can frost come in Sullivan's Island?
In half of years the last 32°F night comes after March 13; in one year in ten it comes after March 30. Waiting until March 30 leaves about a one-in-ten chance of a later frost.
Nearby and next
- South Carolina climateThe statewide normals and every place in the state
- Charleston City, SC4 miles from this station, 67.2°F a year
- Charleston, SC14 miles from this station, 66.5°F a year
- Summerville, SC29 miles from this station, 63.8°F a year
- Edisto Island Middleton Plantation, SC29 miles from this station, 66.7°F a year
- Compare two placesMonth by month, side by side
Download these normals (CSV) · JSON · How these figures are made