There's a lot of blog posts about the barometric pressure headaches, and the connection it has to hydrocephalus that are either pretty long, or hard to understand so I'm going to try to avoid both.
There are two studies that I've found online that explains this problem. The first explains in scientific terms the exact point barometric pressure gets high enough that it effects ICP (intracranial pressure). The second one explains that the cerebrum either increases in size or decreases in size depending on the weather including stormy weather, but also when it comes to temperature or humidity. To be more specific the rest of the brain stays the same size, but the cerebrum changes sizes. In stormy weather, the heat, and when it's humid the size increases. But in cold weather it decreases. So if your barometric pressure headaches are worse in the summer than the winter, this might explain why. Also I live in Arizona where it normally doesn't get too cold. So between that and other desert weather patterns. I would like to eventually like to visit a colder State in the Fall to see how much more of a difference it makes when it comes to my headaches.
I also found a source while researching for this post explaining that barometric pressure issues might just be lethargy, which I've experienced far longer than the headaches itself. I noticed it as a teenager because of my age, but probably dealt with it during stormy weather long before that. My headaches started when I was 22. and I've definitely made up for not really having them in childhood during the last 12 years. Lethargy is of course is the minimum for barometric pressure headaches. The other end is headaches that so bad that you can't get out of bed when you might normally have a very high pain tolerance.
Sources are below, and I'm including more of a experience that a guest blogger wrote for me years ago.
https://pubmed.ncbi.nlm.nih.gov/33839865/
https://waltersdegree.blogspot.com/2017/09/did-you-know-some-interesting.html?m=1
http://timothy-landry.blogspot.com/2015/04/guest-blog-by-mikayla-weather-and-shunts.html
