Squalls:

Never parley with a squall. Take in sail at once. You can never tell from the appearance of a squall how much wind is in it. The most innocent-looking are generally the most dangerous. I was once on a yacht when a squall appeared that looked more like rain than wind. All hands except the skipper, an old man, decided that it would not amount to much. The skipper, much to our disgust, insisted upon taking all sail off. We had scarcely got the canvas lowered and gasketed before the squall struck, and laid the yacht over on her side and kept her there until the blast had spent itself. The force of the blow was terrific; probably the air was traveling at the rate of 70 or 80 miles an hour. A large lumber-laden schooner close to had her foresail blown clean away and lost part of her deck load. This taught me a lesson I have never forgotten.