Fish don't usually fall from the sky, but this unusual meteorological phenomenon is possible although rare. The best explanation for this odd occurrence is that strong air disturbances, such as tornadoes, can lift water and fish up into the air. Then, the tornado can carry them for some distance. When the tornado becomes weaker, its energy is not capable of holding objects up off the ground any longer, and it begins to rain fish. This can also be referred to as "animal rainfall," but often, the event is simply described as "raining fish."
A tornado is a very strong wind that twists around itself. The inside of the tornado, known as the vortex, contains calm air. The outside air moves upward and around the calm center. The air at the bottom of the tornado is constantly moving upward, so as the air moves, new air is pulled up after it. This draws in objects underneath the tornado and sends them upward.
Fish live in water, but tornadoes usually begin over land. If the tornado then moves over water, it can create what is known as a waterspout. Instead of pulling air upward, it pulls water upward. Fish in the water can also be drawn out at the same time.
Waterspouts can move at speeds of up to 100 miles (161 kilometers) an hour. This means that fish can travel far away from their original location. The waterspout can only maintain its violent energy temporarily, and when it loses momentum, it can rain fish. Fish may, surprisingly, survive the waterspout and the fall to the ground. If the air inside the tornado is cold enough, the fish may also freeze.
The meteorological phenomenon of waterspouts does not just have the capability to rain fish. Over the centuries, there have been reports of skydiving frogs, crayfish, and lizards. Stones can also fall from the sky.
One report from the mid-1900s even tells the story of a rain of candy. Most of the unusual rainfall items can be traced back to water sources. With items falling from the sky, another more mundane possibility is that they were dropped from an aircraft.
A feature of events that rain fish or other items is that usually only one type of object falls on one area. Scientists suggest this is because each item differs in weight and size from others. The lighter and smaller objects tend to be carried for longer periods than heavy and large objects.