a lot depends upon where you are going. First off it will be very hot and very muggy, secondly August is prime hurricane season especially in the Eastern Caribbean. You would be better off choosing a Southern route during this time of year.
August is hurricane season in ALL the Caribbean and Gulf of Mexico. The height of the season is late August through early October. But, if there is a storm, the ship will go around it. You may see some ports in different order or a totally unexpected port.