Very timely post.

I too get nasty headaches post-rides but now that you mention it, I haven't had a single one all winter. I was bed-ridden yesterday afternoon after my first hot and fairly long (64 mile) ride yesterday due to head pain. Excedrin did very little to help and that's quite unusual for me. I too am quite adept at remaining well hydrated and while my nutrition was off yesterday, there were no other unusual occurances outside of the exertion and the heat.

I did a little survey/research on a fitness site I belong to last summer and many felt that they were perhaps exertion headaches. These are typically triggered by an elevated HR for extended periods (and only for some people). If this were true, it would certainly explain why they are so prevalent in warmer months as I've noticed that my HR level remains naturally lower on colder rides. The only advice I got was to head them off with medication before they got out of hand. I found that for my longer rides last year, when I had about 1/3 to 1/4 of the distance/time left to ride, I'd take Excedrin. That seemed to keep the pain at bay (and I'd completely forgotten yesterday).

That said, I also have issues with heat rash that I cannot seem to prevent, so it may just be heat-related. I'm a northern girl living in a hot southern environment!