There is no federal tax exemption on mortgage interest. There is a tax deduction. You are allowed to deduct mortgage interest on your main home and one second home, up to a maximum indebtedness of $750,000. If your total indebtedness is less than $750,000 and these are your only two homes, then the interest on both is deductible on federal schedule A, and you don’t have to worry about which home was your main home at which time of the year.
If there is a special state tax benefit for a mortgage, then you will have to consider the rules of that state. I’m not familiar with those particular states. However, if you only get a benefit for your main home, your main home is where you live most of the time. It is determined by the facts and circumstances of your life and can’t be arbitrarily chosen for a larger tax benefit.
