Do I need to wear a helmet in California?

I''m fifteen going on sixteen in a couple of weeks. Is it illegal to ride w/o a helmet at my age? I have all the other stuff I need on my bike: lights, reflectors, etc...
Update: In case it is illegal, what are the chances of a cop deciding to pull me over?
Update 2: that would be lying.....but i like it :P
10 answers 10