We just went for July 27 to Aug 1.
It was cool, upper 60's, and VERY FOGGY. However, I have to admit, I choose a cruise that headed north, like to Canada, hoping that it would be on the cool side for the middle of the summer.
At boarding time from Halifax, there was a sudden down pour. It didn't last long, but what really impressed me, was that Carnival had a person handing out towels to passengers as they re-boarded. I thought is was one of those little but very thoughtful things.
Did I mention it was VERY FOGGY?