Why does my dog react to approaching rain

I have a 10 year old Shih Tzu who is terrified by thunder and lightning. She will hide under the bed or go upstairs and hide in a small room. Can’t get her to go upstairs otherwise. Recently she goes and hides when there is no thunder but with the approach of even spotty shower type clouds. Somehow she senses their approach.
Any one have an idea of how or what she senses? Could it be an atmospheric electric potential or ionization of some sort?

WAG: I can smell rain coming on sometimes, with their much more sensitive noses, dogs can probably smell it much better and much more consistently.

There are many theories as to what triggers storm anxiety. It’s possible that the dog hears the storm long before we do. It’s also possible that they can sense changes in atmospheric pressure.

If your dog seems to be really bothered by it, talk to your vet about medications you can give her when she starts getting scared. I’m sorry to say it, but storm anxiety usually gets worse as the dog gets older. My dog started out being mildly afraid as a young dog, and now at ten will shake, cry and try to stuff herself beneath furniture when a storm is approaching.

My vet prescribed a series of different anti-anxiety medications. Just like people, it sometimes takes a while to find the right one. My dog responded well to Valuim, so now whenever she starts acting very nervous, I give her one and she’s fine. It’s really made things better for her.