You won't find much variance in Hilton Head's weather—it's a great place to visit year round. Colder months hover somewhere around 60°, whereas warmer months get to the high 80°s.
Going to Hilton Head, you'll fly into one of two airports: the Hilton Head Island Airport (HHH, which is about 5 miles from the resorts) or the Savannah/Hilton Head International Airport (SAV, which is about 45 minutes south). You can rent a car at either airport, or catch a taxi, ride-share, or shuttle. Getting around Hilton Head itself is best by car and bike, and there are a ton (60 miles) of bike trails depending on how much you want to exercise.