I have sailed in late August twice, once a Hurricane passed by Florida prior to the cruise in 2011. Rough seas the first night to the point where we were rocking a Main Dining!! Younest son and me were not happy.
Unfortunately CC and Nassau got hit bad. So, no Castaway.

So we docked at Nassau on CC day but you could not get off of the ship. That night we went back out to sea and docked at Nassau, as scheduled the next day, all excursions were cancelled but you could get off the ship.
My family of course were a little sad, it was our 2nd
DCL and it was only a 3 Night on the brand new Dream. So, we made the best of it. You can not go wrong being on a brand new disney ship....AquaDuck, mini golf etc.
The 2nd time was in 2014 very late August, no worries. Weather was warm, but the same as home in NJ. The prices were so low for late August that I snagged a Concierge Family Stateroom for $2800 for 4. We got a Cabana and everything. You will never see that price again. We had a fantastic time.
So, just like some guest will get an early May 100 degree week at WDW. August is hit or miss with the weather. Prices in late August, I am guessing are still good. I know early September seems to be a good time too for the price.
Happy Sailing.
