3rd Or 4th?

Riddle me this: why would a town hold 4th of July fireworks on Tuesday July 3rd rather than on Wednesday July 4th (the actual holiday?) I've heard of them being held the weekend before, but what's the point on a different weekday? That is what the next town from mine is doing this year - fireworks on July 3rd and a parade on July 4th (my town doesn't do anything.)