Los Angeles: Geography and Climate

Los Angeles lies on a hilly coastal plain with the Pacific Ocean as its southern and western boundaries. The city stretches north to the foothills of the Santa Monica Mountains and is bounded by the San Gabriel Mountains to the east. Numerous canyons and valleys also characterize the region, making it an area of diverse climatic conditions. The predominant weather influence is the warm, moist Pacific air, keeping temperatures mild throughout the year. Summers are dry and sunny—the city averages 329 days of sun per year—with most of the precipitation occurring during the winter months. Smog and air pollution are common problems, gathering in the coastal basin during periods of little air movement. Other unusual weather phenomena include the Santa Ana winds, which bring hot, dusty winds of up to 50 miles per hour from the surrounding mountains, and the occasional flash floods in the canyon areas, causing mudslides.