Probably California…
As far as the East Coast goes, it depends on what you consider extremes. Up here in MD we say that, if you don’t like the weather, wait 5 minutes. I know that VA, MD, DE, PA, and to some extent NJ and southern NY have similar climates, though of course the southern end of these sates tends to be milder in the winter and hotter in the summer. Last summer in MD was rainy and mild. This summer has been beautiful…at least up till August. I don’t consider the winters harsh…I usually wish for more snow! Give me a blizzard any day! Fall and spring can be screwy, spring more than fall. Sometimes the temps get down into the 40’s at night in late April. I would say that the mid-Atlantic states are probably the most moderate in the east coast.
“Throw your heart over the fence and your horse will follow.”