Big Bear Lake is a reservoir in the San Bernardino Mountains in San Bernardino County, California, United States. It has an east-west length of approximately 7 miles (11.2 km) and is approximately 2.5 miles (4 km) at its widest measurement, though the lake's width mostly averages a little more than 1 mile (1.6 km). These approximations are based on the lake having an optimum retainable water level. At dam's end Big Bear measures its deepest water at 72 feet (22 m). It is a completely snow-fed lake having no other means of tributary or mechanical replenishment.
According to the National Weather Service, the warmest month at Big Bear is July, when the average high is 80.7°F (27.1°C) and the average low is 47.1°F (8.4°C). The coolest month is January, with an average high of 47.1°F (8.4°C) and an average low of 20.7°F (-6.3°C). There are an average of 1.2 days each year with highs of 90°F (32°C) or higher. Freezing temperatures have occurred in every month and occur on an average of 193.0 days each year. Lows of 0°F (-18°C) or lower average 1.1 days each year. The highest temperature recorded at Big Bear was 94°F (34°C), last recorded on July 15, 1998. The record lowest temperature was -25°F (-32°C), on January 29, 1979.