Another plus of starting in summer is that you won't have the stress of classes on your for a little while. Hormones can give you some ugly mood-swings, and it's best to experience those (or know whether or not you will be experiencing them) when you aren't around anyone except for the people who are closest to you, who will be understanding.
I'm just playing devil's advocate here, but timing HRT so as to prolong keeping your transition a secret seems like a mixed idea. The only people who are going to notice development are the ones who know you well, and you will have to take the plunge eventually-for me, HRT was the only thing that pushed me to go full time, and I'm very happy I did...plus (and I'm not sure how old you are), when you start hormones can make a huge difference; if I had started just six months earlier, my chances at passing would have been much higher, and I really regret that failure.
Whatever people say, HRT WILL NOT make you look like a woman alone, unless you're starting it at a far younger age, or have hit the genetic lottery...you will just like you did before, with slightly softer features, small breasts, and a slightly more feminine figure. I've been on hormones for a year and a half, and I have no breasts whatsoever-my advice is not to build your transition plan around the notion that hormones will make you look amazing before you go full time. That usually takes years of hormones, surgeries, and mad skills with a brush and blowdryer!
