Santa Ana winds are a Southern California weather phenomenon that most commonly appears in in autumn, but can occur at any time of year. Onshore wind normally brings cool air (and often a “marine layer” of low clouds) from the ocean, making the coast much cooler than inland. But when a “dome” of high pressure air settles over the Great Basin, it pushes hot and very dry air from the Nevada and Utah desert through gaps in the mountains east of Los Angeles, reversing the normal weather pattern. The entire Los Angeles area endures a heat wave, but the coast is hottest (and smoggiest). Santa Ana conditions typically make September and October the hottest months of the year in Southern California.
The combination of heat, high winds, and very low humidity can create devastating wildfires. And people well away from any flames can suffer respiratory, nasal, and sinus problems from the smoke and low humidity. But as a kind of compensation for all the misery, the smoke and smog Santa Ana winds blow out to sea can produce particularly brilliant sunsets. This example, photographed in Rancho Palos Verdes, California, was during a Santa Ana condition in January that produced pleasantly warm temperatures but no fires. Nature took advantage of the smog and a layer of high clouds to make an Abstract Expressionist painting on a canvas of sky and ocean.