As most of the country swelters this week, San Francisco residents are pulling on their jackets and turning on the heat. The city is experiencing a winter-like chill, with temperatures in the 50s– about 10 degrees below average. And then there’s the fog, which has delayed flights at the city’s airport.

We know you’ve heard this on many occasions, but we also know odds are you’ve promptly  forgotten it each and every time. So once more — impress your friends at parties and informal meteorological gatherings! — here’s why it’s so frickin’ cold in San Francisco:

The chill is in part a result of San Francisco’s location between the ocean and the Central Valley, according to Diana Henderson, a forecaster with the National Weather Service Forecast Office for the San Francisco Bay Area/Monterey. To the west, the marine layer sits above the cold Pacific. To the east, heat in the valley creates thinner air and low pressure.

The valley becomes like a vacuum that wants to be filled by the heavier marine layer. It pulls that layer over San Francisco, which typically makes the city cooler than other parts of California — and the country — in the summer.

This week, Henderson said, an additional low-pressure system has moved in from the north, which is keeping cooler air around. She said temperatures should warm up later this week.

Meanwhile, San Francisco residents are bundling up against the chill. Here are some of their tips for dealing with the cold.

Why It’s Chilly in San Francisco 17 July,2012KQED News Staff

  • Nicki

    I visit my Mom in Chicago, then come back to thoroughly enjoy the San Francisco chill after sweating non-stop for a week.

  • I prefer Karl to “marine layer” but beggars can’t be choosy. Thanks for the mini-biography.

  • no better place to live…

  • I LOVE it. Wouldn’t want to be ANYWHERE else on Earth in the Summer!!!

  • i do my annual complaining….

  • Kati Quibell

    Layers, layers, layers is the way to dress anytime you are visiting San Francisco. You never know the sun MAY come out at some time and you want to be prepared.

  • Blueman5

    After 29 years in SF, although I love her, I am overjoyed to be out of the incessant chill. I do not miss the biting wind that comes off the Pacific. Although my new neighbors and I are baking in record heat in Minneapolis, I love walking the streets at night without a sweater or jacket over my shoulder. Free! Free at last!

  • Anonymous

    What? I love it here. I don’t see a problem. If I wanted to live in sweltering heat, I would move back to Jersey.

  • Greg M

    I understand all of this but why does it only happen in San Francisco? I can assume that further south (Southern California), the Pacific is not as cold but the inland areas do heat up. But why not north of the Bay Area where the inland valleys heat up and the Pacific is cold?

    • Dantesque

      It does happen. LA beaches are 30 degrees cooler than valleys. It’s just much less harsh because no other city has the unique position at the tip of the wide open Golden Gate, which is like a massive wind tunnel sucking that cold air and fog inland.

    • Dantesque

      Oh and north of the Bay Area, certainly the Mendocino coast is cool and foggy while say, Ukiah, is baking in the summer

  • Boone

    Dealing with the San Francisco cold? Complain. A lot.

  • Suzanne

    Watch the weather news across the country and be grateful.

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