Fruit Bats near Sydney, Australia, July, 2008. (Photo/Curtis Foreman via Flickr)

While satellites, computers and measuring stations are now used to forecast the weather, many farmers around the world used to rely on Mother Nature’s signs. Some still do.

In Australia, for example, ants building nests on top of fence posts or turtles leaving rivers en masse were considered signs that the heavens were about to open. A bright red sunset meant the following day would be fine.

So, what’s the significance of tens of thousands of bats falling out of the sky over the weekend?

That just means it’s stinking hot.

Authorities in the northeastern state of Queensland have blamed a heatwave for the deaths of about 100,000 flying foxes from 25 colonies, many of which literally fell from the sky.

“It’s a horrible, cruel way to die,” Louise Saunders, a conservation worker, was quoted as saying.

“Anything over 43 degrees [Celsius, 109F] and they just fall. We’re just picking up those that are just not coping and are humanely euthanizing what we can.”

RSPCA spokesman Michael Beatty said the high temperatures were a “catastrophe” for the local bat population.

“That’s obviously going to have a pretty disturbing impact on those colonies and those colonies are vital to our ecosystem,” Beatty said.

The sudden mass deaths are also causing local residents considerable discomfort as the stench from the rotting carcasses intensifies in the heat.

Thousands of bats are lying dead in trees and bushes. Efforts are being made to collect the thousands of carcasses, but many have been left so as not to disturb nearby colonies.

Health authorities have warned residents not to touch the furry creatures amid fears about the spread of virus.

At least 16 people are already receiving anti-viral treatment after close encounters.

This article originally appeared in GlobalPost.