According to the United States Census Bureau, the city has a total area of 41.7 square miles (108.0 km²) of which 36.2 square miles (93.8 km²) of it is land and 5.5 square miles (14.2 km²), or 13.14%, is water.
Lake Elsinore, originally Laguna Grande, is the largest natural freshwater lake in Southern California and is situated at the lowest point within the 750-square-mile (1,900 km2) San Jacinto Watershed at the terminus of the San Jacinto River, where its headwaters are found on the western slopes of San Jacinto Peak with its North Fork, and Lake Hemet with its South Fork. Lake levels are healthy at 1,244 feet (above sea level) with a volume of 30,000 acre·ft (37,000,000 m3) that often fluctuate, although much has been done recently to prevent the lake from drying up, flooding, or becoming stagnant. At 1,255 feet (383 m), the lake would spill into the outflow channel on its northeastern shore, known properly as Temescal Wash, flowing northwest along I-15, which feeds Temescal Creek, which dumps into the Santa Ana River just northwest of the City of Corona. It then flows to Orange County, out to the Pacific Ocean just south of Huntington State Beach.
Lake Elsinore is bordered by the Elsinore Mountains to the west, which are a part of the larger Santa Ana Mountain Range, and receive a few inches of snowfall a few days each year. Included in the Santa Ana Mountains is the Cleveland National Forest and El Cariso. Lake Elsinore is north-west of Murrieta and the northern portion is part of the Temescal Canyon.
Lake Elsinore is a city which encompasses a large geographical area. To better distinguish the wide range of neighborhoods, the city is organized into 11 districts. Each district beholds its own unique geography, culture, age, and history which together make Lake Elsinore a very diverse and culturally rich city. They are the Alberhill, Ballpark, Business, Countryclub Heights, East Lake, Historic, Lake Edge, Lake Elsinore Hills, Lake View, North Peak, and Riverview Districts