I don't get it – Upweather - beautiful weather Review

I was recommended this app as a way to check for fog before going to the beach. I'm sitting on the coast in San Luis Obispo covered in a thick marine layer / fog and the app says the skies are clear. Does it not show fog? Am I not using it properly? Is it a useless app? Dan
Review by The yogpodder on Upweather - beautiful weather.