Blame the wind, if you want. In Southern California they call it the Santa Ana; in the north, the Diablos. Every autumn, from 4,000 feet up in the Great Basin deserts of Nevada and Utah, air drops down over the mountains and through the canyons. By the time it gets near the coast it’s hot, dry, and can gust as fast as a hurricane. Or blame lightning, or carelessness, or downed power lines.