well think about it this way, if the SST that far south are still in the upper 80s and low 90s, how could August SST be even warmer than that? It's probably that the temps get that hot in August and stabilize near there until October. Thats how you get cat 5s coming out of the GOM in October like Michael and also going into Central America or even into the Southeast.
https://en.wikipedia.org/wiki/List_of_Category_5_Atlantic_hurricanes#Listed_by_month
6 of them in October, almost the equal of August (7), and significantly trailing only September (21). The first Cat 5 in the historical records is actually an October hurricane. Heck, there's even a November Cat 5 in that list!
Michael, Matthew, Mitch and Wilma were all famous October Cat 5s.