My dog had a similar problem. She would try to hide, she would pee, she would poop, she would run around the house tearing things apart and knocking stuff over, etc...

I partially solved her fear by talking to her in a calming voice and making a bit of a game out of the noise.... everytime I would see the lightning I would say "here it comes, get ready, here comes the boom" in the voice I use for playtime.

Essentially, by playing this game, she learned that the boom comes after the flash. Once she learned that she was less afraid because she would expect a loud noise after the flash, so it wasn't an unexpected noise that startled her.

After she got used to the concept of flash=boom she was still a bit afraid of storms, but instead of being a terror in the house she would just sit and look out the window and whine a little bit... but she stopped peeing, pooping, knocking things over, etc...

The funny thing is that I got the idea to teach her about flash=boom from a neighbor who had a 3 year old child. She taught her daughter about flash=boom in thunderstorms so that the little girl would stop crying, and amazingly enough the same concept worked for the dog (of course it took longer to teach the dog since the child understood english and the dog did not)
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