While the bitter cold makes life uncomfortable above ground, it appears it is causing problems below the surface, too.

In emails and tweets to CP24, residents from various parts of the Toronto area, including York and Peel regions, Oshawa and Rexdale, said they were awakened overnight by thunderous booms that they believe were caused by cryoseisms, also known as frost quakes, in the frozen ground.

Some viewers said the loud booms startled them and shook their houses.

Police in York and Peel regions said they received dozens of calls from people who were alarmed and wanted to know what was going on.

In Peel Region, police fielded about 100 calls from concerned residents and some thought they heard an explosion, gunshots or falling trees.

“Some people even called in and said a person was breaking into their house,” said police spokesman Const. George Tudos.

Most of the calls in Peel Region came from Brampton, Bramalea and north Mississauga between midnight and 5 a.m.

Officers were dispatched but they quickly came to the conclusion that “it was all the same phenomenon” that people were hearing or feeling, Tudos told CP24.

Similar noises were heard earlier this week and Christmas Eve.

Frost quakes explained

Frost quakes are a rare event in the GTA and they occur when ground water freezes and the ice expands, cracking the rock or earth and creating an explosive expansion of air, said CP24 meteorologist Bill Coulter.

Geoff Coulson, a warning preparedness meteorologist with Environment Canada, said he is not aware of any dangers to the public from frost quakes.

Coulson said the national weather agency has been seeing more reports about frost quakes, largely due to people's use of social media.

“This is something that we’re seeing more of,” Coulson told CP24 reporter Jamie Gutfreund. “Some of them can be quite strong but they do tend to be quite localized.”

In the GTA, the temperature dropped to about -23 C overnight with a wind chill of -35.

@ChrisKitching is on Twitter. For instant breaking news, follow @CP24 on Twitter.