The climate is Mediterranean, so it tends to be windy and cold throughout much of the park. During the summer months, fog is common along the coastlines. Dress in layers is recommended. Hiking boots are appropriate in some areas. Comfortable shoes are also recommended within the San Francisco area, which are most comprised of asphalt or concrete.
Maine ocean islands provide the only nesting sites for Atlantic puffins in the United States. Eastern Egg Rock in the midcoast region, Seal Island and Matinicus Rock at the mouth of Penobscot Bay, and Machias Seal Island and Petit Manan Island off the downeast coast provide habitat for more than 4,000 puffins each summer.