The City of London was among a number of communities to set a new record low overnight.
The temperature very early Monday hit -30.5 C, smashing the record of -24.4 from Feb. 16, 1963.
In Sarnia, the overnight low hit -28.3 C, breaking the 2004 record of -21.2, while Wiarton hit -34.3, breaking a record of -25.6 set just last year.
More records fell across southwestern Ontario, from Windsor to Waterloo to Welland, amid extreme cold warnings issued by Environment Canada.
Those warnings have been lifted, but a cold weather alert issued by the Middlesex-London Health Unit remains in effect until Tuesday.
