When rain is combined with thunder, thunderstorms occur. Visible lightning can also occur during thunderstorms, along with hail or strong winds. These storms occur when heat in the lower atmosphere pushes large amounts of hot air and humidity into the colder, upper atmosphere. The hot air intensifies and forms an unstable cloud. When precipitation falls from this cloud, it creates a downward airflow that spreads throughout the ground as strong winds. Lightning occurs when ice particles in the storm cloud collide with each other and generate large amounts of electrical charge. The sound of thunder is a side effect of this lightning. When struck by lightning, the atmosphere expands rapidly around the electricity, which can cause low roaring thunder and then reunite, causing loud thunder cracks.
