The topography of Los Angeles is diverse. The landscape ranges from beach to mountain, from desert to woodland. The Los Angeles area divides distinctly into the Los Angeles basin, which includes most of the city, the surrounding San Gabriel and San Fernando valleys, and the backdrop of high mountain ranges.

Los Angeles' weather is greatly affected by topography. The climate within the city varies widely. Summer temperatures can range from a cool 68 degrees Fahrenheit on the coast to 80 degrees or 90 degrees Fahrenheit only 20 miles inland. During the winter, heavy rains are common and a single storm may drop as much as 3 inches of rain in an hour.

The San Gabriel Mountains in the Los Angeles area cause special weather conditions. Here, moist air masses move inland from the Pacific and are cooled as they meet and rise over the mountains. This cooling produces heavy rainfalls on the windward slopes. This is called the orographic effect. The eastward mountain slopes are in a rain shadow, hence rainfall is much less.