Floods occur when water submerges dry land, and can be caused by heavy rainfall or other phenomena like storm surges from tropical cyclones. Some safety precautions for floods include assembling disaster supplies, evacuating if at risk, never driving or walking through flooded areas, and waiting until it is safe to return after a flood has receded. People should also be alert for flash flood warnings, climb to high ground immediately if warned, and use caution entering buildings after flooding.