Temperatures in the London region will plunge more than 20 degrees in less than 24 hours, according to Environment Canada forecasters, as a cold front moves in, ushering a return to minus double-digit temperatures. 

Forecasters are calling for temperatures to fall to -9 C by Friday night, marking a 20 degree shift from the comparitively balmy 11 C London was basking in early Friday morning. 

The double-digit warmth melted much of the city's snow pack that had accumulated over more than two weeks of extreme cold temperatures since Boxing Day.

The big melt broke up thick ice along the Thames River, causing ice jams and flooding along certain parts of the waterway. 

Adelaide Street bridge, London Ont.

The view of the Thames River beneath the Adelaide Street bridge, where an ice jam had collected in a spot where the waterway burst its banks thanks to steady rains and temperatures as high as 11 C. (Colin Butler/CBC News)

By Friday morning, the temperature plunged 14 degrees in seven hours, from 10 C at 4 a.m. on Friday morning to -4 C at 11:00 a.m.

Tonight, forecasters are calling for a low of -18 C as another cold snap seems to be settling on the London region.

Saturday will see temperatures stay steady at -11 C through the day with a chance of snow and Sunday will see sunny skies and a high of -12 C. 

Ice jam

A close up of an ice jam that formed Friday beneath the Adelaide Street bridge in London's east-end after temperatures rose to 11 C Thursday, breaking up thick ice that formed on the Thames River after nearly two weeks of extreme cold. (Colin Butler/CBC News)