Was the A/C or defroster on? If yes, that means the belt if heavily loaded when it fails. Water lubricates the belt and it slips, gets hot and fails very quickly. Install a splash guard to keep water off the belt. One other thing . The pulley’s are worn out. They don’t last forever. Especially the one on the crankshaft. This makes the belt far more prone to slipping when wet…The worn pulley can no longer grip the belt properly.