Sea water temperatures have an effect on general weather. In the Gulf of Mexico, they feed tropical weather systems during Hurricane season, making them grow into stronger storms, much faster than they would over cooler water.
I asked Meryl about the Mediterranean, because it may be a factor in the hot, humid weather Italy is experiencing.
CD
I looked it up, the sea in the bay of Naples is 23C at the moment.
Don't know how to send the link.
We re going through the "Anticiclone Africano", which would normally arrive later July/August.
That's why we have yellow/grey skies, no wind or breeze, just stagnant, sticky air.