If you looked up in the sky and saw an ominous hole in the clouds – or several – don't worry, they're not aliens.
The meteorological phenomena are referred to as "fallstreak holes," but have also been called "hole-punch" clouds.
It's a term to describe a rare occurrence when water droplets in clouds become "super-cooled" below zero degrees, setting off a process where a circular part of the cloud turns to ice crystals and falls as precipitation.
The result? Swiss-cheese skies.
"They're pretty impressive in that you're seeing a fairly large geometric shape all of a sudden in the sky," said Environment Canada Meteorologist Armel Castellan. "Some people describe them as 'saucers' that are invading."
Pink/purple “O” gap #yyj #cityofvictoria #sunrise from the #GallopingGoose trestle bridge. pic.twitter.com/kPt14l1Icy
— armel castellan (@armelcastellan) January 28, 2019
MODIS satellite imagery today captured some "fallstreak hole clouds" (a.k.a. hole punch clouds) forming over British Columbia and we've had some reports of them drifting over counties to our north this afternoon in northwest flow aloft. #wawx pic.twitter.com/4NlXec8mAc
— NWS Seattle (@NWSSeattle) January 28, 2019
The fallstreak holes were spotted over Greater Victoria, Nanaimo and one so big over the Fraser Valley that many wouldn't have noticed it was a hole, Castellan said.
He said the process of water droplets turning to ice crystals, known as the Bergeron process, can be replicated in an experiment in your own kitchen.
By placing bottled water inside a pot of super-cooled salt water, you can rapidly change water to ice in seconds, he said.
