
Hi Janet,

Sounds exactly like mine.  Same circumstance, same onset symptoms, 
same cafergot uselessness, same duration.  In fact, of all the people
I know who have migraines, none have been so similar.  There is such
a wide variation between people with respect to what causes their
headaches, that I generally don't bother sharing what I've learned
about mine, but since ours seem to be alike, here are my observations.

I don't think it's heat, per se (I've had more in winter than summer).
Dehydration could conceivably figure, though.  Try tanking up before
playing rather than after.

Being in shape doesn't seem to help me much, either.

I've identified four factors that do make a difference (listed in 
descending order of importance):

1) Heavy exercise
2) Sleep deprivation
3) Fasting		(e.g., skipped breakfast)
4) Physical trauma	(e.g., head bonk)

Heavy exercise has preceded all of my post-adolescent migraines, but I 
don't get migraines after every heavy exercise session.  One or more of 
the other factors *must* be present (usually #2).  Since I discovered 
this, I've been nearly migraine-free -- relapsing only once every two 
or three years when I get cocky ("It's been so long, maybe I just don't 
get them anymore") and stop being careful.

Hope this is helpful.