precipitation falling with an intensity in excess of 0.30 inches (0.76 cm) per hour
Short periods of intense rainfall can cause flash flooding, longer periods of widespread heavy rain can cause rivers to overflow.
There was also heavy rain, and the accident occurred on a road that was notorious for hydroplaning.
heavy rain led to destructive flash floods throughout the Phoenix, Arizona area Monday morning.
Though in 1971, the balloon portion was cut due to heavy rain.