Hi Staying Positive! (What a great name)
I have to write to you on this subject, because this is something I dealt with just 4 days ago! We had a big thunderstorm here where I live. Last summer I was somewhat okay with them, at one point when I was living alone, I was out on my apartment balcony watching the lightening and listening to the loud thunder, thinking, wow this is something. Over this past winter, my anxiety had gotten a lot worse, worse than it had ever been, (at one point I wasn't capable of leaving my bed) so, it was pretty bad! Storms hadn't even crossed my mind until I saw the weather report and saw the words "scattered thunderstorms" I was freaking out! (and I have been doing VERY well with my anxiety lately)
I think us lovely people with anxiety are afraid of the weather for 2 reasons. The first reason being it's something big we can't control, whether it be the noise of the thunder or the random strikes of the lightening. It is something that happens that we have zero control over - that is what makes us anxious about it! You know that expression, "Ya can't control the weather!" Well, we don't like to hear that we can't NOT control ANYTHING!

The second reason being the outcome of that loss of control, whether it results in a panic attack or scattered lawn furniture around your yard. We are ALWAYS worried about what could happen to us, our family, our homes, our town, etc. due to this big thing that happens that we have no control over.
Here is a different way of thinking about it. I like to replace my thoughts with better, more positive ones, and with your name (staying positive!) I'm sure you wont object to this! First and foremost, fully realize that this is the season for thunderstorms and there is nothing you can do about it. And that's okay! We don't need to control everything, and I will tell you why we want to. We want to control everything, because we are terrified of what could happen if we lose control, for example, a loved one getting hurt as a result of the storm! Keep this in mind though, it is not common for a thunderstorm to cause major damage. Make sure you've got your children in the house in a safe room (if the storm is bad enough) and you will be safe and snug as a bug in a rug. The only bad thing that could possibly happen is you have loud rumbling thunder! Say to yourself, "Ok, thunderstorms are just a part of the season, no amount of worry and fear is going to prevent them from happening, nothing bad is going to happen if we have a thunderstorm, I can handle this, I can do this!"
Something I did a few nights ago when the thunder was loud here, is I crawled into bed, turned my fan on high, and watched a movie on my laptop with my headphones. I could barely hear that loud, pesky thunder! I did some deep breathing and repeated to myself, "I am okay, it's just a thunderstorm, no big deal, nothing bad is going to happen" (because it's true, nothing bad is going to happen!) After about an hour, I was able to come out from under the covers and move my location to the couch, right by the patio door, and that thunder didn't bother me much anymore! I think for us, it is the unknown of things starting, but we do get used to them and that fear can't last forever, our brains get tired of keeping it going.
I know this sounds like insensitive advice, but as soon as you are fully capable of saying and admitting to yourself that no amount of fear is going to prevent the storm from coming or prevent anything bad from happening, and the chance of something bad happening is VERY slim to none, you are going to be able to get over it so much faster. I'm not telling you to get out there and enjoy that storm, but you can learn to co-exist with them without getting upset about them.
And remember, it always passes. A storm doesn't last forever. At the most an hour or if it's really big, 2 hours. But I promise you, you can handle 2 hours of being uncomfortable. We are anxiety, we've dealt with worse than 2 hours, am I right? hehe.

And also, think of the benefits of a storm and the rain, it's great for all those beautiful blooming flowers to get a drink of water.
You can do this! No big deal.