Hi Hopefully...
I used to get dreadful 'migraines'...wouldn't go away until I started to flow, would sometimes happen right before I ovulated, sometimes during the lull I used to have in my regular cycle; flow for a couple days, stop, horrible headache that nothing would touch, start flowing, headache lessened. So yep, I think it is definitely hormore related. My prob now is that I spot for a week or so before and after my cycle, which is still 25-28 days, but much lighter. Aahhhh, the joys of being a girl!! As for the weather setting them off, I have sinus probs too, and I think I've acquired allergies in my 'old' age, so I pretty much have a dull headache until that settles down anyway...but its a different kind, not as severe as my 'hormone' headaches were.
I hope your headache gets better

Conni