The extreme cold weather is causing unusually loud side effects in parts of southern Ontario. Peel Regional Police received about 100 calls Thursday night from residents concerned about loud booms. Experts say they were likely hearing a phenomenon known as frost quakes. Natural Resources seismologist Cathy Woodgold says when water in the ground freezes, it needs extra space as it expands. A sudden drop in temperature can build up tremendous pressure because there’s no room for the expanding ice and something will suddenly crack, causing a loud bang. Similar noises were reported throughout the Toronto area on Christmas Eve and December 30. An Environment Canada meteorologist says to his knowledge, the frost quakes are not dangerous, just loud.