Can it really rain frogs—and spiders, worms, or other critters? It may not be common, but it happens. Learn more about what causes this wild weather phenomenon.
Rainfalls of animals have been recorded for centuries, with some of the oldest records dating from 77 AD by the Roman Pliny the Elder. While these stories of falling fish, frogs and bugs are strange, over the past two centuries scientists have confirmed that they do occur. Let’s start with frogs …
What Causes Raining Frogs?
The most common explanation is that updrafts, particularly “watery” tornadoes aka waterspouts, suck the critters up into the sky. When the wind weakens, the animals fall. (We see a similar explanation for “blood” rain, where updrafts picked up red dust from the Sahara.)
As frogs weigh so little, they’re easily lifted into a waterspout which is a whirlwind picking up water. These events will happen before a severe thunderstorm when there is a high-pressure system. The center of the waterspout is a low-pressure tunnel within the high-pressure cone.
Just think of a tornado on land and how it can lift homes. A passing tornado can literally empty small ponds of water so it’s not really that surprising that other small animals or even salt and stones can be sucked up into a waterspout.
When the storm loses its energy and the pressure drops, the clouds will release rain—as well as frogs and small fish and whatever else it picked up in its travels! Apparently, a waterspout has even been known to rain tomatoes!
Image: A 1557 woodcut showing a rain of frogs in Scandinavia. Public domain
Not many years ago, Norway experienced an April rain of worms. Biologist Karsten Erstad reported thousands of live earthworms scattered across the surface of the snow when he was out skiing. This is the time of year that worms start to emerge from the ground, so scientists speculate that the worms were swept up by the strong winds common in the mountainous areas of Norway and carried to snowy slopes.
Last April, Norway had a rain of worms. Source: lacounty.gov
There was a different explanation for a recent May rain of millions of spiders in Goulburn, Australia. (Shudder!) As anyone who loved the children’s book Charlotte’s Web knows, many species of baby spiders “balloon.” They weave parachute webs that catch the breeze and spread the youngsters throughout the territory. Apparently, the population was going through a spell of fertility.
In May, Australia had a rain of spiders. Source: Wikipedia
Raining Germs and Microbes
As creepy as the recent worm and spider rains may be, they are pleasant compared to the “germ rains.” Dust from Africa’s Sahara Desert is carried by trade winds across the Atlantic. While this is a valuable source of minerals for downwind vegetation, it also appears that germs and microbes hitch a ride. Scientists have not correlated any human outbreaks (other than asthma in the Caribbean), but they have traced at least one coral disease to heavy dust storms.
Germs, spiders, worms! It’s enough to make a person buy an iron-plated umbrella.