These incredible ‘light pillars’ appeared over Alberta last week

When the temperature plummeted in Canada last week, these otherworldly light pillars appeared over Blackfalds, a city in Alberta. It may look like the entire city is about to get abducted by aliens, but this phenomenon actually has a simple, frigid explanation.

North America experienced its first deep freeze of winter last week. From Canada to the Upper Midwest, brutally cold temperatures plowed in from the Arctic — and more specifically, Siberia. The air from Siberia can be some of the coldest in the world, and has acquired the nickname “Siberian Express” thanks to the way in which it charges over the North Pole (what meteorologists refer to as “cross-polar flow”) and spills into the Lower 48. It often brings dangerous, life-threatening and record-setting cold temperatures.