North America is a continent entirely within the Northern Hemisphere and almost all within the Western Hemisphere. It can also be considered a northern subcontinent of the Americas. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the west and south by the Pacific Ocean, and to the southeast by South America and the Caribbean Sea.
North America is a very large continent which surpasses the Arctic Circle, and the Tropic of Cancer. Greenland, along with the Canadian shield, is tundra with average temperatures ranging from between 10 to 20 °C (50 to 68 °F), but central Greenland is composed of a very large ice sheet. This tundra radiates throughout Canada, but its border ends near the Rocky Mountains (but still contains Alaska) and at the end of the Canadian Shield, near the Great Lakes. Climate west of the Cascades is described as being a temperate weather with average precipitation 20 inches (510 mm). Climate in coastal California is described to be Mediterranean, with average temperatures in cities like San Francisco ranging from between 57 to 70 °F (14 to 21 °C) over the course of the year