Air conditioning does most of the drying in a building on this coast, and it only runs part of the year. At Grand Strand Airport, inside the city, April through October carries 1,974.3 of the 2,003.3 cooling degree days in a normal year, 98.6% of the annual cooling load in seven months. From November to March the systems mostly idle, and the air does not: over the last decade of observations at that airport, mean daily relative humidity averages 78.4% in December, and every month averages above 72%.
The shoulder season is when the trouble gets set up. A unit closes in October with the thermostat pushed up to keep the bill down, nobody opens a door until March, and with the cooling off the inside drifts toward the outdoor number instead of the 30 to 50% the EPA suggests indoors. Spring then brings sea fog, warm wet air cooling over an ocean still cold from winter, and the first guest of the year walks into a room shut since fall.
Turn-on week is our busiest commercial run in North Myrtle Beach. A management company wakes a block of units in March, finds two with a smell and one with staining inside a closet, and the first booking is three weeks out. The same problem in July costs the owner nights nobody can sell. Hurricane season runs from 1 June to 30 November, so the fall close-up usually follows a wet stretch; Horry County’s flooding pages show what your building is exposed to.