Terrified of tornadoes

Ever since I was a little kid I've had the biggest fear of tornadoes. I never used to have a problem with thunderstorms until the first time the sirens went off, I was about 8 years old and it was a really bad storm. Now I hate thunderstorms and I even get fearful when it rains because I don't want a possibility of a tornado. I also dread Spring and Summer every year and have considered moving to somewhere like Alaska, since I live in the Midwest (USA) and we get a lot of tornadoes.

I hate the sirens more than anything. They give me the chills and I even freak out during practice runs when it's sunny out because I hate how they sound. Every time there's a tornado warning I run to the basement and basically cry my eyes out. If there's a storm scheduled I'll refuse to leave the house and will haul my favorite things to the basement. I'm 20 and people tell me I overreact and sometimes they get annoyed with me, but I don't know how to stop being so scared. Is it normal?

*Note: I've never actually been in a tornado, but they always come really close to my area. I think they usually get anywhere from 20-40ish minutes away and then dissipate.