For the third day in a row, a new record high temperature was reached in Sarnia.
Environment Canada said the mercury peaked at 23.9 C, 75 F, at Chris Hadfield Airport on Monday, surpassing the previous record high for November 9 of 23.1 C, 73 F, set in 1999.
Weather agency figures indicated Sarnia was the warmest spot in Ontario Monday.
Record high temperatures were also reached on Saturday and Sunday as an air mass, more typical of late summer, affected the region.
The stretch of record-setting temperatures is expected to continue Tuesday across southern Ontario.
The weather agency said a cold front will move through the region Wednesday, bringing an end to the warm conditions.