Why is it 20 degrees hotter at my hotel than at the beach?

San Diego runs two climates at once. A shallow layer of cool marine air pushes onshore overnight and holds the coast gray and mild well into the morning, while neighborhoods a few miles inland clear earlier and heat up fast. This is not a rare event. It is the default pattern for much of the year, heaviest in late spring and early summer, and it is why a hotel in Mission Valley or El Cajon can be running 85°F while La Jolla Shores sits in the low 70s at the same minute. It matters well beyond what to pack. If you're choosing where to live, you are choosing which of the two climates you get every morning — people who buy a coastal address for the view sometimes find themselves under cloud cover more mornings than they expected, and people inland trade the gray for real summer heat. Our live reading pulls current conditions from National Weather Service stations on both sides of the split, so you can see today's actual gap rather than an average.