Great Lakes form a single, naturally interconnected body of fresh water, within the Great Lakes Basin. They form a chain connecting the east-central interior of North America to the Atlantic Ocean. From the interior to the outlet at the Saint Lawrence River, water flows from Superior to Huron and Michigan, southward to Erie, and finally northward to Lake Ontario. The lakes drain a large watershed via many rivers, and are studded with approximately 35,000 islands. There are also several thousand smaller lakes, often called "inland lakes," within the basin. The surface area of the five primary lakes combined is roughly equal to
Great Lakes on Lake Ontario's northeast shore. Related to the lake effect is the regular occurrence of fog over medium-sized areas, particularly along the shorelines of the lakes. This is most noticeable along Lake Superior's shores. The Great Lakes have been observed to help intensify storms, such as Hurricane Hazel in 1954, and the 2011 Goderich, Ontario tornado, which moved onshore as a tornadic waterspout. In 1996 a rare tropical or subtropical storm was observed forming in Lake Huron, dubbed the 1996 Lake Huron cyclone. Rather large severe thunderstorms covering wide areas are well known in the Great Lakes during mid-summer; these