Why did the old man know there would be a breeze all night?

Santiago is so attuned to the natural conditions in his environment that he is able to predict what the weather will be like by through observation. On the night before he landed the big fish, he noticed that "the sky was clouding over to the east and...it looked now as though he were moving into a great canyon of clouds and the wind had dropped". He rightly predicted that "there will be bad weather in three or four days...but not tonight and not tomorrow"

"There were high cumulus clouds and enough cirrus above them so that the old man knew the breeze would last all night............"