How can I get over a fear of thunderstorms/lightning/heavy rain

Yeah... Its thundering at my house... I don't like thunder :(

Try learning what it really is. Understanding what your afraid of often helps one not be afraid of it. Also if you're inside a car, home, shelter, etc.. There's really not much to worry about it's loud and can be scary, but it can't hurt you so just ignore it.

EDIT:
Not to mention if you learn what it is it's pretty neat stuff, and next time somone asks "What's Lightening?" you can proudly tell them

Hey...I'm scared to...but don't worry...we have lilapsophobia...it's the fear of thunderstorms...you know you have it if you can't stop monitoring and worrying about weather...you can't overcome it...just do something that makes you comfortable...like for me it's walking around my house with my dog...hope this helps!!!

Look at it a different way. It's nothing but a big noise, it means nothing. Try watching a movie comedy, or reading the book, it really sets the mood for those activities.

well the first step is accepting you have a problem. second is facing the problem like the big kid you are. :D