In every season you will see something interesting but in Winter it is to cold for some people( but who love skiing will come to us in Winter couse we have really good conditions for not a high price) so as Andy said in first post one of the best times is Summer couse of Euro 2012  and also we have 2 seas Black and Azov Which is used  for sun and sea toursim <img title="Laughing" src="http://www.italki.com/Scripts/tinymce/jscripts/tiny_mce/plugins/emotions/img/smiley-laughing.gif" alt="Laughing" border="0" />

I would say the best time to visit California depends on if you are visiting Northern or Southern California! It is amazing and beautiful weather in Northern California with so many activities to do in the late spring and summer. In Southern California it is over 100 degrees F in the summer, so I would say spring or winter. Those are the times I visit Southern California and it is beautiful weather (I usually visit in winter). In central california there are some wonderful places especially of you love surfing ;-) Santa Barbara is extremely gorgeous in the summer! In northern california the seasons to avoid are winter (so rainy!) and early spring (also rainy). It is only perfect of you want to go skiing in Tahoe...something that I do every winter :-) 

Anytime 

Definitely winter. I am living in a middle-seized mountain range, which looks stunning when it's covered in snow. 

I`m from San Sebastián, in the nort of Spain. The best time to visit my city is in summer(but rain a lot).