Is there a website that will tell me whether it is sunny or foggy at Ocean Beach in San Francisco?

I love biking to the beach, but when it's sunny in my neighborhood (the lower haight) and looks like a great day for a bike ride, I never know if I will hit the fog belt as soon as I get to golden gate park. Is there a site that tells me current fog conditions for different parts of the city so that I can know if it's worthwhile to bike to Ocean Beach? Or Baker Beach?