Forgive me if anything I post in this reply repeats information from others. For several years I have noticed that my HA activity worsens each fall season as early as August lasting until late november. it also seems to follow barometric pressures both high and low seem to trigger HA activity.

In addition: Last summer on the 4th of July my programmable shunt was actually scrambled when a lighten strike came down very near me. I was not struck directly but the ground strike was so close that it fried the transformers and surrounded me and others near me in a blinding white/yellow flash of light that was simultaneous with the thunder clap. It actaully moved my setting, jamming it between 2 settings. So most assuredly I do know that weather force can have some affect on our shunts; the only question is how much.

BTW--luckily the shunt was able to be reset without replacement though at first it looked like a surgery situation.