Yes it is normal. I don't know how far north into South Carolina they get, but all of coastal Georgia has sand gnats.
Get a nice smokey fire going and that will clear them out quick. This time of year, they can be bad if it isn't too hot or too sunny. When I work in the yard, I always get a little fire going and make sure it smokes while I am outside. If I'm not paying attention, I know when the smoke stops, because the gnats come back pretty quick.
Deet works well too, but I hate sitting around smelling like Deet and getting it on everything I touch. When the kids have sporting events this time of year and in the fall Deet is pretty much the only thing to do. Generally I wear long pants and long sleeves if I'm going to be outside during gnat times and put 40% deet on my face and neck. It usually takes to coats to be completely effective.
When we first moved down here, I was amazed at the number of people that wore pants and long sleeves when the temp dropped below 90 degrees. If the temps are above 50 and below 90, the sand gnats will be out. Now I know why they wear pants and long sleeves when the temps are in the 80s. Move 20 miles or so from the coast and they seem to disappear.
-Michael
