Madeira has a mild climate all year round!
In the south coast during the summer the average temperature is about 25 º, and during the winter of 4 or 5 degrees less.

As far as the water temperatures range from 18 º to 25 º in winter to late summer. The good thing is that there is no thermocline, the temperature that you will find on the surface will be the same even at 30 meters!