Average temps range from low 40's to low 60's for Feb. By mid Feb, the normal temps are usually in the mid 60's with some days of 75 or higher.
The ocean is usually not higher than 60 during the month, so ocean swimming is only for the very hardy. The resort pools are heated and can be a lot of fun with a nice day.
The resort has a full slate of activities and there are lots of dining and shopping options available on the island itself. There are several interesting historical areas to visit, as well as galleries. The weather is usually OK for golfing and tennis year round.
It all depends on what your expectations/needs are, as Hilton Head has something for everyone- except a Disney Theme park.
Enjoy your trip!