Of course, you probably haven't woken up to such a grisly scene. You probably haven't been driving around in a storm and had your car pelted with what you thought was hail but turned out to be frozen frogs. But other people have. While it's not the most common weather phenomenon in the world, it's not as rare as you might think. It happens all over the world, at least since the first century A.D. -- when the Roman naturalist known as Pliny the Elder described the event -- and as recently as 2005 in Serbia.
You might hear a report of raining frogs -- and other unexpected objects, some not even organic -- at least once a decade or so. Amphibious rain seems to be picking up in frequency. In the last 20 years, newspapers have found more opportunities than ever to write about frogs falling from the sky. For unknown reasons, Britain appears to be especially susceptible in recent years. The cause of frog rain in general is less mysterious, although still a bit of a brow-furrower at times. It's also just as gross as many of us imagine. That final scene in the 1999 film "Magnolia," which left most movie goers jaw-droppingly disgusted and a little impressed, is apparently a pretty accurate portrayal of the phenomenon, according to newspaper accounts.
In this article, we'll find out what's actually going on when frogs rain down and what happens when they fall from the sky. Incidentally, frogs aren't the most common creatures to accompany rain. You'll understand why when we look at the process of frog rain on the next page.
But our first question is the most obvious one: How in the world do the frogs get up in the sky in the first place?
Frog Rain Causes: The Flight of the Amphibians
It's hard to get a good mental picture of frog inundation that doesn't have Moses standing off in the distance. The biblical image of a slimy, surprising mass is tough to avoid. However, there's actually a pretty simple explanation for the whole thing: It involves whirlwinds and low-weight creatures.
Frogs can weigh as little as a few ounces. But even the heavier ones are no match for a watery tornado, or a waterspout, as it's called when a whirlwind picks up water. The series of events that can lead to frog rain go something like this:
A small tornado forms over a body of water. This type of tornado is called a waterspout, and it's usually sparked by the high-pressure system preceding a severe thunderstorm.
As with a land-based tornado, the center of the waterspout is a low-pressure tunnel within a high-pressure cone. This is why it picks up the relatively low-weight items in its path -- cows, trailer homes and cars get sucked up into the vacuum of the vortex. But since a waterspout is over water and not land, it's not automobiles that end up caught in its swirling winds: it's water and sea creatures.
The waterspout sucks up the lower-weight items in the body of water as it moves across it. Frogs are fairly lightweight. They end up in the vortex, which continues to move across the water with the high-pressure storm clouds. When a particularly powerful storm hits land, the waterspout might go with it.
When the storm hits land, it loses some of its energy and slows down. The pressure drops. Eventually, the clouds release the water they're carrying. As the rain falls, the vortex eventually loses all the pressure that's keeping it going, and it releases whatever it has picked up in its travels. Sometimes, this cargo includes frogs.
The end result is frog rain. Sometimes it's a few dozen frogs -- or a couple hundred or even thousands. And usually, it's not just frogs. Frogs get top billing because of their role in Exodus, but waterspouts can carry all sorts of items. So what's the strangest thing that can fall from the sky? Find out next.
Other Weather Phenomena: It's Raining Tomatoes
Frogs can travel tremendous distances in the vortex of a waterspout. Waterspouts can move across hundreds or thousands of miles, although that's extremely rare. It's more common for frogs to travel just a few miles before they fall to the ground.
Reports of strange objects falling from the sky are numerous and varied. People have reported raining squid, worms and fish. Fish are actually the most common creatures to fall from the sky, for obvious reasons -- they're very lightweight, and they're the most common water inhabitants [source: BBC]. But waterspouts can pick up heavier objects, too.
Waterspout winds can spin at amazing speeds -- up to 200 mph [source: CMMAP]. These types of wind speeds can pick up a very wide range of cargo because they can suck up objects from up to 3 feet (1 meter) below the surface, and the low-pressure core they form is an extremely powerful vacuum compared with the speeding winds surrounding it. Large water birds have also fallen from the sky. At least one source reports a sailboat coming down with rain [source: CMMAP]. Presumably a waterspout can pick up a few things when it hits land, too, because it has also been known to rain tomatoes and coal [source: CMMAP].
But it's when the frogs, fish and other water animals hit the ground that things really get gross. It's unlikely they survive the journey, what with the speeding low-pressure vortex and the impact once that vortex dissolves. Usually, the frogs die, although it's unclear when exactly that happens -- during the trip or as a result of the fall.
However, sometimes the frogs luck out. When it rained frogs in a small town in Serbia in 2005, people walked outside after the storm to see their streets blanketed in frogs trying to hop their way back to water.
For more information on frog rain and related topics, look over the links on the next page.
Related HowStuffWorks Articles
More Great Links
- Can it really rain fish and frogs? CMMAP. (Cool Experiment!) http://littleshop.physics.colostate.edu/docs/CMMAP/tenthings/FishAndFrogs.pdf
- Freak Incidents. BBC Weather Center. http://www.bbc.co.uk/weather/weatherwise/living/severe/
- How can it rain fish? BBC News.com. August 20, 2004. http://news.bbc.co.uk/2/hi/uk_news/magazine/3582802.stm
- It's raining frigs in Serbia. Sci-Tech News24. July 6, 2005. http://www.news24.com/News24/Technology/News/0,,2-13-1443_1717510,00.html