From what I understand, it can depend on their application deadline? For example, schools that had a December deadline, you can expect to hear something around February. UT Health San Antonio had a deadline of February 1st (relatively late compared to some of the others), so maybe March?
I saw a blog post where someone said most acceptances take place January/February and rejections are sent in March but I don't think that's 100% true (if you consider the deadlines).
Hope that helps and good luck to you too!