14 year old behaviorist in training

Make a tape of thunder sounds.  Start playing it a low volumes, have your dog sit, or lay down, then praise and reward him.  Slowly increase the volume over time.  Understand that this may be a  long process.  I would also recommend that you yourself research fear based behaviours in dogs.  What ever you do, DON'T comfort him.  Good luck,

thanks, you are one of the nicer people i've met here.
seriously thinking of leaving though.

I had a fountain that had rainstorm sounds on it. I set it up beside my dog's crate when he was a puppy, and I turned the fountain on full force and the sound up loud so it sounded like a thunderstorm to get him used to the sounds. You could get something like that, and start it at a very low volume and slow flow on the fountain, and turn it up louder and harder as your dog gets used to it.
Last year during the Fourth of July Fireworks, we took Max with us. I just kept him working on his commands, and fed him really good treats. As a result, he loves the fireworks. We take him with all the time to the fireworks, and when we get fireworks at the store we take him out with us. I've got the wacky dog now who loves the loud noises.When we took him with us to the New Years Fireworks, he was actually watching them. To get your dog used to them, I would buy some small ones at the store. Get someone to set them off while you work with the dog at a comfortable distance, or if you can't do that, get some and set them off, and record it. Then you can play the recording at a low volume while you work with your dog. Gradually increase the volume of the fireworks, or if you have someone set them off, you can move closer as your dog becomes comfortable with them.

If you really want to start working toward being a behaviorist ( and I am assuming working with animals).  Go to the library.  Take out a copy of Karen Pryor's Dont Shoot the Dog. 
After you have read it, read it again.  Then another time, then another time.  Read it until you can almost recite it from memory.  That will give you a very good understanding of the theory of behavioral psychology without all the really technical names and such that you encounter in college level classes.

thanks