SAN FRANCISCO -- You couldn't blame Northern Californians if they seemed a bit crazed over the whipsaw of whacky weather patterns they endured over the weekend.
As one weather system moved across the region Saturday, it sent temperatures into the 100s in inland areas, but San Francisco residents kept cool thanks to the city's natural air conditioning.
The National Weather Service says the high temperatures just outside of Walnut Creek -- a suburb about 25 miles northeast of San Francisco -- hit 112 degrees on Saturday. In nearby Brentwood, Contra Costa County fire officials say after paramedics were called to an outdoor high school graduation ceremony after one person had fainted emergency crews ended up treating about a dozen people for heat-related problems.
Forecasters say other inland areas also saw temperatures break 100 degrees on Saturday, with the mercury hitting 111 in Napa County and the hottest spot in Monterey County saw a high of 108 degrees.
Meanwhile, breezy winds blowing off the Pacific Ocean and San Francisco Bay kept San Francisco residents cool as cucumbers over the weekend, with temperatures in the upper 60s both Saturday and Sunday.
But for people who didn't live in San Francisco or near the beaches, they flocked to coastal areas for relief.
Traffic was jammed on Interstate 80 into San Francisco throughout the day Saturday as people drove to the city and nearby beaches to escape the heat. To the north, the California Highway Patrol reported a one-hour wait for traffic getting off Highway 101 and on to Highway 1, a scenic coastal drive along Marin County's beaches.
But as one weather system moved out of the region, a second system moved in late Sunday bringing cooling relief with a dramatic drop in temperatures to inland areas, fog to the beaches and thunderstorms across the area.
Temperatures on Sunday were in the 70s most inland areas -- about 30 to 35 degrees cooler than the day before.
And powerful thunderstorms -- a relatively rare occurrence along the coast of Northern California -- were reported across the Bay Area Sunday night.