Such occurrences have been reported in many countries all over the globe in human history, in many cultures: from the Roman empire to Asia, both America and Africa... from ancient times to modern days. The phenomenon is present in literature and popular culture, for example the English language has the famous words "it's raining with cats and dogs", but similar examples can be found in many languages over the world.
The most common animals fallen from the sky are the frogs and the fishes, but there have been seen rains of toads, snakes and worms.
One hypothesis explain the phenomenon using the strong winds that travel over the water and pick up creatures as fishes and fogs or small other animals like snakes and worms while passing over the land. These winds would carry them several kilometers and drop them when they lose their strength... but this phenomenon has never been scientifically tested or witnessed. French physicist André-Marie Ampère was among the first scientists to take seriously accounts of raining animals - one of the versions of this hypothesis was explained by the physicist to the Society of Natural Science.
More recently, a scientific explanation for the phenomenon has been developed that involves tornadic waterspouts or tornados capable to capture and carry objects and animals to high altitudes and transport them over large distances. The strong winds involved in the phenomenons are capable of carrying the fishes over wide area and, later, allow them to fall in localized areas. The hypothesis is supported by the type of animals in these rains: small and light, usually aquatic. Also, the rain of animals is often preceded by a storm - the waterspouts or the tornado is losing its energy and water first, before losing the animals. The theory does not explain the various species of animals involved in each incident - according to the theory the animals should be only from one or a few species (for example fishes and frogs or toads), but in fact it's a group of similarly sized animals.
Sometimes the animals survive the fall, suggesting the animals are dropped shortly after extraction. In other cases the product of animal rains is not intact animals but shredded body parts.
Some sci-fi fans might even say that the space is stumbling around one point and it forms shortcuts (the well known worm holes) that capture and carry small animals from several locations to the center of the phenomenon, but it's not somenthing that can (easily) be scientificly proved.
The source the image is here.
