Yellowstone Lake is the largest body of water in Yellowstone National Park. The lake is 7,732 feet (2,357 m) above sea level and covers 136 square miles (350 km2) with 110 miles (180 km) of shoreline. While the average depth of the lake is 139 ft (42 m), its greatest depth is at least 390 ft (120 m). Yellowstone Lake is the largest freshwater lake above 7,000 ft (2,100 m) in North America.
In winter, ice nearly 3 ft (0.91 m) thick covers much of the lake except where shallow water covers hot springs. The lake freezes over by early December and can remain frozen until late May or early June.