According to the United States Census Bureau, the city has a total area of 30.2 square miles (78.2 km2), of which, 30.2 square miles (78.1 km²) of it is land and 0.02 square miles (0.1 km2) of it (0.05%) is water.
Temecula has a Mediterranean climate (Köppen climate classification Csa). August is typically the hottest month of the year with December being the coldest month. Most precipitation occurs from November to March with February being the wettest month. Winter storms generally bring moderate precipitation, but strong winter storms are not uncommon especially during “El Niño” years. The driest month is June. Annual precipitation is 14.14 inches. Morning marine layer is common during May and June. From July to September, Temecula experiences hot, dry weather with the occasional North American monsoonal flow that increases the humidity and brings isolated thunderstorms. Most of the storms tend to be short lived with little, if any rainfall. During late fall into winter, Temecula experiences dry, windy north-eastern Santa Ana winds. Snowfall is rare, but Temecula has experienced traces of snowfall in recent memories. A rare F1 tornado touched down in a Temecula neighborhood on February 19, 2005.