Your peak times are going to be
Whenever Spring Break/Easter Falls during the year...the week of Memorial Day, June, July and August, the week of Thanksgiving and the week before and the week of Christmas as well as the week of New Years.
Off season is generally January (after New Years), February, and into March (Depending on when Spring Break and Easter falls). Then again the end of August, Spetember, October, the begining of November and the begining of December.
Pretty much anytime that school is out is going to be higher priced as that is when the demand is there.