The period for which the colleges are closed for vacation, for the same period the professors are also provided vacation. Although this period may not be entirely a holiday, but it may happen that you have to do some gradings in the vacation or if the professor is involved in research then he/she may have to do about it. But in general, there will be vacation and you will have to join the college after the summer vacation.

I hope this answer helps. All the very best for your future endeavors!