It depends on your age. If you are 16 you have to wear a helmet. But if you want your head to get blown off that's on you. It is safe to wear a helmet for protection.
Washington state law says yes. and since you'll be invinceable with it on you don't legally have to have insurance. but with our weather who wants to drown on a bike anyway?
Whether or not you are legally required to wear a helmet is a matter of state law. Each state has different requirements, with some states requiring you wear a helmet if you are over 18, over 21, or...