Check out this map at the Epicurious site. You can find what's in season for any month in any state.
I haven't visited the Epicurious site much lately, but they have added lots of features related to seasonal eating, now comparing favorably to the BBC Good Food site. AND - you don't have to translate the seasonableness. (We in northern California are a little ahead of Britain in harvest times, but have a shorter season for cool crops.)