Late September or Early October signals the beginning of Santa Ana winds, which may continue intermittently through the winter. Early Santa Anas are often responsible for coastal San Diego's hottest and driest days of the year. Records show that 62 percent of the days at Lindbergh Field with 90-degree readings or higher have occurred during the months of September and October. The desert-like days are a consequence of dry air from a high-pressure area centered over Nevada or Utah moving across southern California's coastal mountains toward a low pressure area offshore in the Pacific Ocean. West of the mountains the air sinks as it rushes toward the coast, heating (by compression) about 5 1/2 degrees Fahrenheit for every 1000 feet of descent. During a full-blown Santa Ana, gale-force winds rake the foothills downwind of the mountain passes, and San Diego's coastal communities often experience temperatures that are among the nation's highest.
Escaping the heat of this season's first couple of Santa Anas will not be easy -- if you can't be inside air-conditioned buildings, that is. Along the coastline, where temperatures may reach the 90s, taking a dip in the surf solves the problem. Inland, the furnace-like heat is moderated only by increases in altitude. Head for the highest elevations of the county-- the mile-plus heights of the Palomar and Laguna Mountains, for example. You could climb a couple of the county's loftiest peaks: Cuyamaca Peak (6512') in Cuyamaca Rancho State Park, or Boucher Hill (5438') in Palomar Mountain State Park. On peaks such as these during a Santa-Ana-wind episode, the thermometer registers about 25-30 degrees lower than in the lowlands. Since the early phase of a Santa Ana sweeps away atmospheric water vapor and air pollution, hundred-mile vistas in every direction may be yours to enjoy.