Sullivan's Island, SC climate
Sullivan's Island has warm winters and warm summers, with plenty of rain. A typical July afternoon reaches 90°, a January night drops to 41°, and snow is almost unheard of.
NOAA 1991-2020 climate normals Updated once a decadeWhat a year in Sullivan's Island feels like
Winter
Spring
Summer
Fall
Sullivan's Island weather by month
Average highs, lows, rain and snow for every month, from NOAA’s 1991–2020 normals.
| Month | High | Low | Rain + melt | Snow | Wet days | Snow on ground | 30-yr range |
|---|---|---|---|---|---|---|---|
| January | 59° | 41° | 3.3" | 0.2" | 9 | 0 | 45° – 55° |
| February | 61° | 44° | 3.1" | 0.1" | 9 | 0 | 45° – 60° |
| March | 67° | 49° | 3.4" | 0 | 8 | 0 | 53° – 65° |
| April | 74° | 57° | 3.2" | 0 | 8 | 0 | 61° – 70° |
| May | 81° | 65° | 3.2" | 0 | 8 | 0 | 70° – 77° |
| June | 87° | 72° | 5.4" | 0 | 12 | 0 | 75° – 84° |
| July | 90° | 75° | 6.0" | 0 | 13 | 0 | 81° – 85° |
| August | 88° | 75° | 6.5" | 0 | 13 | 0 | 79° – 84° |
| September | 84° | 70° | 5.5" | 0 | 10 | 0 | 75° – 82° |
| October | 77° | 60° | 4.5" | 0 | 7 | 0 | 65° – 73° |
| November | 68° | 50° | 2.9" | 0 | 7 | 0 | 54° – 65° |
| December | 62° | 44° | 3.2" | 0 | 9 | 0 | 43° – 63° |
| Year | 75° | 59° | 50.0" | 0.3" | 114 | 0 |
“Wet days” have at least 0.01" of rain or melted snow. “Snow on ground” counts days with 1" or more. The 30-year range is the coldest and warmest that month’s average temperature got between 1991 and 2020.
Rain and snow in Sullivan's Island
Sullivan's Island gets 50 inches of rain and melted snow a year. August is the wettest month and November the driest. Rain or snow falls on about 114 days a year.
About 321 frost-free days a year
In half of years the last 32° night comes by February 4 and the first one by December 30. That leaves about 321 frost-free days for gardens, longer than 96% of U.S. towns.
Heating and cooling a home in Sullivan's Island
Engineers use “degree days” to estimate how hard a furnace or air conditioner works. In Sullivan's Island, 40% of that work is heating and 60% is cooling, so air conditioning is the bigger bill.
Degree days measure how far each day’s average temperature falls below or rises above 65°, added up over a year. Source: NOAA station normals.
Sullivan's Island and its neighbors
Sullivan's Island borders 2 towns with climate data. January nights across them vary by 0.3°. Isle of Palms has the coldest January nights (41°) and Mount Pleasant the hottest July afternoons (90°). Sullivan's Island’s January low is 41° and its July high 90°.
Temperatures and rain come from NOAA’s 5 km grid, so each town gets its own value.
How Sullivan's Island compares
Compared with every U.S. town and city on TownTapestry, each counted once.
Warmer than it used to be
The last 30 years in Sullivan's Island averaged 1.4° warmer than the 1900s. The biggest change is in December (+2.6°). The shift is larger than in 60% of U.S. towns.
Change by month1991–2020 average minus 1901–2000 average, at Sullivan's Island’s spot on NOAA’s grid
How much a month can swing
A normal is an average, and real years wander around it. December swings the most: between 1991 and 2020 its average temperature ranged from 43° to 63°. July is the most reliable, staying within 4°.
Common questions about Sullivan's Island’s climate
What is the coldest month in Sullivan's Island?
January, with a typical high of 59° and a low of 41°.
What is the hottest month in Sullivan's Island?
July, with a typical high of 90° and a low of 75°. About 25 days a year reach 90°.
How much snow does Sullivan's Island get?
Almost none. A normal year brings 0.3 inches.
When is the first frost in Sullivan's Island?
In half of years the first 32° night comes by December 30, and the last spring frost by February 4.
What is the rainiest month in Sullivan's Island?
August, with 6.5 inches of rain and melted snow. The year totals 50 inches.
Temperatures and rainfall come from NOAA’s gridded climate normals for Sullivan's Island itself (about a 3-mile square). Snow, frost dates and day counts come from NOAA’s weather station at Charleston Intl Airport, SC (15 mi, snow) and Charleston City, SC (6 mi, frost, heat and degree days). Normals are 30-year averages, not a forecast. Source: NOAA NCEI U.S. Climate Normals, 1991–2020 and 1901–2000.