Spider rain: it may sound like the key plot-point of a low-budget horror movie, but the faintly ridiculous (and very disturbing) scenario of spiders falling from the sky is real, and it’s not even that uncommon. Stories and videos of arachnids filling the air have been shared as far afield as Australia, Texas, and Brazil, but what causes these bizarre weather conditions – and could it happen near you?
What is spider rain?
Spider rain is just as surreal as it sounds. An event in which hundreds or even thousands of spiders fill the sky and “rain” down on those below.
Though it may sound unbelievable to most people, spider rain is actually pretty commonplace in certain regions of the world. The residents of Espírito Santo do Dourado, a town in the South-eastern region of Brazil, claim that “spider rain” is a regular part of their lives. In fact, the locals are so used to the apocalyptic weather that it doesn’t even register as an unusual event. The now-viral footage of the town’s spider rain was originally captured and shared by a teenager who was visiting town to see his grandparents.
And it’s not just Brazil. Spider rain is also a common occurrence in Australia, and large numbers of airborne spiders have also been reported in Tennessee as well as Texas. But what causes spider rain, is it dangerous, and, most importantly, how likely is it to happen near you? Continue reading to find out!
What causes spider rain?
It may sound like your standard biblical plague, but spider rain is actually the result of a natural (and surprisingly, not uncommon) behavior of several spider species.
What appears to be spiders falling from the sky is actually a mass ballooning event, in which hundreds of arachnids climb up to the tops of trees and fence poles, lift their rear ends into the air and let out strands of silk.
These silken threads catch the air currents and lift the spiders up into their air, allowing them to float up to 4 km in the sky and travel hundreds of kilometers.
Ballooning is a talent many spiders possess. The behavior has been observed in the Linyphiidae (sheet-weaver spiders), Araneidae (orb-weaving spiders), Lycosidae (wolf spiders), and Thomisidae (crab spiders). It is a form of dispersal most often used by baby spiders (spiderlings) to allow them to escape their overcrowded birth sites, where competition for resources can be fierce and cannibalism is often rife.
Spiders need very specific conditions for ballooning including low humidity, warm temperatures, and optimal wind conditions. When “spider rain” occurs, this is usually because a large number of spiders have gathered in preparation to disperse but the weather conditions are not quite right. The spiders hang around until the conditions change and, when the weather is perfect, they all start to balloon at once.
When a mass ballooning occurs, there will often be so many spiders taking off that the sky appears to be filled with them. Sometimes, the weather conditions may change again and unexpectedly carry the spiders back down to Earth, causing them to fall, en masse, on a particular town or region, with the result that it appears to be raining spiders.
Is spider rain dangerous?
Spider rain may sound terrifying, especially if you’re one of the 5% of US citizens with arachnophobia. Fortunately, only a tiny percentage of spider species have venom that’s actually dangerous to humans so, though skin-crawlingly creepy, spider rain is unlikely to actually pose any threat.
Is spider rain likely to happen near you and what should you do if it does?
Nowhere is completely safe from spider rain, and you can probably see the odd spider floating through the air in most parts of the planet. However, “spider rain” where thousands or even millions of spiders fall out of the sky at once is most common in Australia. The phenomenon is most often seen in certain regions of Southern Australia (such as New South Wales) the United States (e.g. Texas) and Brazil.
If you are unfortunate enough to encounter spider rain and want nothing to do with it, the best thing is to take cover indoors until it passes. If you are concerned about spiders getting inside your house, leave windows and doors closed until the arachnids have moved on.
Remember, most spider species pose no threat to humans, and that these eight-legged beasts are a valuable part of the ecosystem. If you encounter spiders in any context, the best thing to do is simply leave them alone.
Rain of animals: toads, worms, and jellyfish
It’s not only spiders that have been known to fall from the sky. Accounts from across the world report much larger creatures such as toads, frogs, fish, worms, jellyfish and even octopi raining down on the Earth.
Incidents of animal rain involving larger, heavier (and, usually, flightless) animals are harder to explain, but scientists believe tornadic waterspouts may be to blame. This is when a tornado forms over water, sucking up and transporting aquatic critters high into the air before carrying them long distances and, eventually, dropping them back down to Earth.
It may sound impossible, but spider rain is not only real but common in some parts of the world. Skies above Australia, Brazil, and some regions of the United States are regularly filled with spiders, which may drift by at great heights or fall, in their thousands, onto the people below.
This horrifying occurrence is the result of a mass ballooning behavior, in which large numbers of (usually baby) spiders will take to the skies suspended from silken parachutes, using the air currents to travel hundreds of kilometers.