It started with a single fish in a parking lot. One day in 2015, employees of the Value Village in Fairbanks, Alaska, were alerted to the presence of a live fish just outside the store. The creepy, eel-like creature had just appeared, as though it had fallen out of the sky. The employees put the 15-inch-long fish in a bucket of water and called the Alaska Department of Fish and Game (ADF&G).

That alone would have made it a strange week for Fairbanks. But the phone at the ADF&G kept ringing. Residents called in sightings of three more fish out of water, including one that materialized on somebody’s lawn.

ADF&G identified the stray fish as Arctic lampreys, a long, parasitic fish boasting terrifying rings of teeth, which it uses to latch on to a salmon, trout, or shark and suck out its prey's blood and body fluids.

Arctic lampreys are common in Alaska waters. They’re less common on land. The fish that turned up that week all bore gashes in their sides, suggesting they’d been picked up by gulls, then dropped once the birds were aloft. The city of Fairbanks is located on a river, and this kind of thing has happened there before. It’s almost surprising that it doesn’t happen more often.

Elsewhere in the world, it does. Stories of freak rains of fish (and sometimes frogs) have persisted for millennia, beginning with Pliny the Elder. Every two years or so, it seems, there’s a plague of airborne fish somewhere in the world. In the last ten years alone, slimy deluges have afflicted citizens of India, Japan, Australia, Hungary, the Philippines, and Ireland.

All of these storms were a bit more substantial* than the drizzle in Fairbanks, sometimes delivering hundreds of live or dead animals. Gulls can’t be to blame for events of that scale. So what is?

The most viable theory at the moment is that these rains are exactly what they resemble: weather. If a tornado or big rainstorm passes over a body of water, it could conceivably suck up some of the pond or river—and the animals that live there with it. As the waterspout passes over land, it dissipates, leaving frogs in the fields or fish at the front door.

However, scientists are not totally satisfied with this theory. For one thing, nobody has ever seen it happen. The fish just seem to appear when we’re not looking. For another, why would a waterspout suck up just one species? There aren’t rains of fish and crabs and pondweed. It’s just fish, and only one kind, at that.

So the mystery remains. All we can do is keep our eyes open and our umbrellas handy.

*With the exception of Ireland, which allegedly experienced a momentary shower consisting of a single lamprey.

All photographs courtesy of the Alaska Department of Fish and Game