Heavy rains may result in the flooding of a basement or a crawl space. In an attempt to rescue possessions or clean up the situation do not walk in or touch this water. The water could be in contact with electrical outlets or extension cords. This would result in you being electrically shocked.
Another potential hazard is a sump pump. This is a submerged motor designed to pump water from one location to another. It has an electric cord going to the motor which is designed to be water proof. If there is a malfunction then you may be shocked by stepping in or touching the water.
Be careful when you are around electrical equipment that might be wet or when being near water that could be in contact with live wiring. When in doubt be safe and consult a professional.