Warm but not too warm. Low humidity. Plenty of sunshine. No measurable snow since 1967. Only a true curmudgeon could complain about San Diego’s weather—California’s second-biggest city is America’s climatic Pleasantville. According to meteorologist Sebastian Westerink of the National Weather Service’s San Diego Office, here’s why.
This article appears in Issue 30 of Alta Journal.
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CURRENT EVENTS
San Diego is on the same latitude as Marrakesh. But the California Current, which transports cold water from British Columbia as far as Baja, is a moderating influence that keeps things cool. Even in summer, San Diego’s sea surface temperatures might hit only 70 degrees, and they serve as the city’s natural air conditioner.
DRY SKIES
Tucked far below the state’s big bend at Point Conception, San Diego is not only the southernmost spot on the California coast but also the easternmost. In fact, the city sits at nearly the same longitude as Boise. That geographic bearing spares it from the worst of the winter storms out of the Gulf of Alaska, which typically lose their punch by the time they travel this far south. So while San Francisco averages around 23 inches of rain annually, San Diego receives only about 10.
MOUNTAIN HIGH
East of San Diego, three subregions of the Peninsular Ranges—the Cuyamacas, the Lagunas, and Palomar Mountain—rise to more than 6,000 feet. The mountain wall is substantial enough to modify frigid polar and Arctic air masses as they move out of the interior of Canada, heating them via compression as they travel along the slopes. And in summer, the high country attracts storms from the Sea of Cortez while San Diego stays protected by its stabler, cooler air.
GO WITH THE FLOW
San Diego’s diverse mesa-and-canyon topography, combined with the city’s proximity to the ocean, helps deliver cooling sea breezes to areas more distant from the coast. As hotter inland air rises, it’s replaced by cool, dense marine air that follows the path of least resistance, flowing like water through whatever gaps it finds in the terrain. The thicker the marine layer, the more pronounced the cooling, delivering relief to inland zones that might otherwise swelter.•
