How do migraines know about upcoming changes in the weather so far in advance?
I think I know how a prodrome can start a day or two before rain or wind or weather fronts arrive. Early changes in barometric pressure could trigger it. But how on earth does my head know three or four days in advance when the predicted changes are still on the other side of the country? Case in point: We have rain and a cold front arriving tonight, so I have a migraine today. And I had prodrome symptoms yesterday — and the day before, and the day before that, and the day before that. It’s Thursday and I’ve had a variety of symptoms all week! Do our neurological systems have a secret connection to the National Weather Service? Do we have super-sensitive barometers in our heads that can pick up the tiniest shifts of isobar toward each other? Are we migraineurs “blessed” with weather-prediction capabilities that NWS, FEMA, NASA and the military envy? If so, they can have it!
Meanwhile, after almost 70 years of chronic daily migraine, I would love to know HOW I apparently know about weather triggers so far in advance. Any ideas?
My opinion? Humans are much more sensitive than we acknowledge.
The subtle changes in air pressure, density, dust, light, etc. can be registered.
I often think if myself as an early warning detection system for other humans.
I more wonder how it is others are oblivious to the things to which I am sensitive.
So, to answer "How?" ....
Because you are a finely tuned human instrument.
I know where you are coming from! I live in Florida and am no stranger to the multiple low pressure systems and storms that roll through here especially in the summer. I agree with glassmind that we are more sensitive than others. I feel as though our thresholds for certain stimuli are much lower than a normal persons. We can be set off by very subtle triggers. I have found some relief, though, with CGRP injections. You may want to get with your doctor and give them a try. Be well! 
I deal with this. I can tell you up to three days beforehand if we're expecting storms in the area, up to 60 miles away. I usually double-check with a housemate as to whether we're expecting storms and when, because that is literally my only migraine trigger.
