Correct me if I am wrong, but I am going to assume that the parade is at night, which is why you are thinking you need a flash.
So I would say that yes, you will probably need it. However, you shouldn't use it.
If you are watching a parade from the side of a street, most on board camera flashes will not be strong enough to light up much of what is going on in the parade. And if you do have a flash that is strong enough, it will probably be distracting to everyone around you.
So when you get there, if everyone else is using a flash and it doesn't seem to bother anyone, then go ahead, but don't expect much. It can't hurt anything, other than drain your battery faster.