According to the United States Census Bureau, the city has a total area of 42.2 sq mi (109.4 km2), comprising 41.5 sq mi (107.4 km2) of land and 0.77 sq mi (2.0 km2), or 1.81%, of it is water.
Simi Valley has a warm and dry climate during summer when mean temperatures tend to be in the 70s.