weather-related migraines

Hi all,
Since childhood, I've gotten one or two migraines a year - a zig-zag aura followed by a mild/moderate headache with slight nausea. Over the past few years, I've gotten the aura with a slight headache or no headache at all. More often than not, the migraines occur in early fall. about a month ago, the weather here in NY suddenly turned fall-like for about a week, and I got several migraine auras with no headache or a slight headache over the course of that week. I also had a runny nose on the days the headaches occurred. I was concerned about the increase in migraine frequency, so I went to see my doctor, who ordered a CT scan that turned out to be normal. The weather warmed up and the auras disappeared for about three weeks. Then from Friday to yesterday, there was a significant drop in temperature and humidity, and I once again had a runny nose and migraine auras. I'm going to see an allergist next week, but I'm curious as to whether any of you have had migraines that appear to be allergy-related or weather-related, and whether there's anything I can do to prevent them. I've always had seasonal allergies, so I'm not sure why I'm suddenly getting more auras. My sinuses appeared clear on the CT scan.