In The Cay, how does Phillip know that its morning while he is blind?

Like many people who lack one of their senses, whether it is blindness or deafness, they quickly learn to use their other senses to cope and survive.  In Phillip’s case, he realizes it is morning while drifting along on the raft because he feels that the wooden boards are cooler.  He knows that the water will cool off the boards during the night because there is no sunlight to warm them.  As Phillip learns to cope with his blindness, he becomes more and more independent on the island and is eventually able to walk around the island using only a cane. As his senses are heightened, he begins to be more self-sufficient instead of totally reliant on Timothy to help him.  In the end, Timothy’s insistence that Phillip become self-reliant saves him after Timothy dies in a violent hurricane.