Vic Bedrossian was commuting to work Monday morning when he saw light pillars in the sky.

He had left Guelph and was driving on Highway 401 near Milton and says he pulled over around 5:40 a.m. to take photos of the optical illusion. He sent the photo to CBC Kitchener-Waterloo.

Another person also observed the phenomenon on Monday and tweeted a photo of it.

A sweet light show this very cold morning heading to work. All lights created a vertical beam into the sky, an effect called Light Pillars. <a href="https://twitter.com/hashtag/Ontario?src=hash&ref_src=twsrc%5Etfw">#Ontario</a> <a href="https://twitter.com/hashtag/Guelph?src=hash&ref_src=twsrc%5Etfw">#Guelph</a> <a href="https://t.co/DR4dFNkftK">pic.twitter.com/DR4dFNkftK</a> —@ryangerritsen

Paul Delaney, a professor of physics and astronomy at York University in Toronto, answered a listener question on the CBC's Quirks & Quarks about light pillars in 2017.

He says the source of the light is generally streetlights or the lights on buildings that are shining upwards into an atmosphere that is "rich, full of ice crystals. Very, very small ice crystals."

The ice crystals then reflect the light toward to the person observing them.

"Ice crystals will tend to form in atmospheric conditions that are relatively calm and, obviously, relatively cold. But we also need to have a lot of what we refer to condensation sites — ice nuclei or dust particles upon which the water vapour, as it gets colder, will be able to condense," he said.