Nantucket is called the Grey Lady for a reason. Fog on the island can disrupt travel plans, especially flights on small planes. One area can be smothered in gray while the other end of the island is bathed in bright sunshine. The beaches are all numbered—good to know just in case of emergency—and note that many do not have lifeguards. Beaches often require off-road permits to drive on; keep the tides in mind so you don't get stranded. Finally, all the cobbled streets can wreak havoc on your ankles (especially if wearing heels), so bring some footwear that has a little support.