Hi there,
While I would encourage you to strongly consider maintaining residency in CA and discussing the long-distance option with your boyfriend (trust me, it IS doable if it's the right person for you and you have really open communication about the challenges involved), I also think, if it's helpful at all, that the weather is something you can get used to! I've lived in California 6 of the last 8 years, as an undergrad and in the working world. I LOVE the weather. I too get migraines before thunderstorms, when air pressure changes, when I'm stressed, and on Wednesdays...... I definitely feel the affects of seasonal depression as well.... but these things can be worked with. 🙂
I've transitioned between east coast, midwest and california multiple times now. I just returned to the east coast to start school again this fall. I considered Davis, but did not realize I had the proper qualifications of "resident" until it was too late in the application process. Had I been a resident, I would have certainly applied. I have done long distance for a few years of my relationship and have been able to make it work (phone, skype, e-mail, visits either once a month or every two months). It is challenging and lonely at times, but for the right person, can really help you in your path. We see this separation time as a chance to fulfill our dreams, support each other through our goals, and return to one another in person, much stronger, more fulfilled and happier people. We just re-initiated the long distance, as I will be starting on the east coast and he is on the west finishing work until at least December (possibly later). We recently got engaged and have no question we want to be together, but our paths are requiring different sides of the country for now. It IS doable. Most important things: a strong foundation (you're sure this is the right person for you) and great communication (no fears about talking about fears).
That being said, I do want to encourage you to consider staying on the east coast. The winter season can be tough, but is an important reminder to slow down, take care of yourself, and have something to look forward to -- spring, summer and fall -- three seasons which can be absolutely marvelous in New England and along the eastern seaboard. I know most migraine sufferers have their own methods of battling migraines and it comes down to finding a routine that works for you. The cold weather is very hard to handle, generally the FIRST YEAR. I found, transitioning from California to Wisconsin in the middle there, the first winter was brutal, I was not properly dressed, the chill was felt in my bones which were not used to the cold. But by the end of the first winter, and when the 2nd winter rolled around, the weather had registered in my bones and I was completely prepared and in fact used to it. I found the snow to be beautiful and dressed in a way that kept me warm at all times, and found it much easier to pass the time through the frustrating dark days. And I really love New England, despite sometimes wishing the warm beach were right down the street, year round.
I guess I just want to encourage you to consider both sides. While maintaining your residency in CA will help you for Davis, certainly consider applying to east coast schools, coming from someone who has had to re-transition between east coast, california, midwest, california and back to east coast...... I've become a pro at the weather patterns to expect, and know that it's quite doable to adjust within a few months to a year of being there.
Whatever you choose, make sure it is the right school for you, first and foremost. If Davis is your dream school, fabulous! If there is a school on the east coast you could love, certainly consider applying there as well!
Best of luck!
J