Expatriots will tell you the late spring and early fall are perfect times to go. It rains a little more often in spring but fewer people are there and the water is warm enough to swim or surf in.

The early fall, such as October would make anyone happy. It stays warm and dry and the water is still fine. The scenery changes (not quite as drastically as say New York), and you can see beautiful colors.

Now, summer is the pinnacle of existence but, if you want to be around fewer tourists but still be able to enjoy the beach, these are the times to go.

As for sites to see, try the lighthouses, especially Hatterass Island's. On a rainy day, skip the movies and head to somewhere like the Graveyard of the Atlantic Museum or the North Carolina Aquarium on Roanoke Island.  If you have kids and the water is too rough, then head to Jockey's Ridge and they will have just as much fun.  Jockey's Ridge is also very beautiful in the evening around sunset.