Did you hear something weird in Toronto last night?
Messages on social media started popping up, around the same time the temperature dropped overnight in the GTA.
That drop in temperature triggers something called a "frost quake."
Essentially, it's an earthquake caused by the freezing of ground water.
"They sound scary, but they aren't. It's just that when we're dealing with these cold conditions the ground water can freeze, and when ground water freezes, it expands and it puts stresses on the ground, so that's why you sometimes hear a loud bang," says Gerald Cheng from Environment Canada.
But he says it's not widespread like an earthquake would be.
"It's very localized, when you talk about an area it affects, it's maybe a block or two, and that's it," says Cheng.
The good news, it appears to be one and done, with temperatures rising into the weekend.