Lambton Public Health has extended its cold alert for another day with the temperature forecast to drop to -16 C (3 F) Tuesday night.
The overnight wind chill is expected to reach -24 C with cold Arctic air entrenched across the region.
Environment Canada meteorologist Peter Kimbell said the mercury dropped to -14.8 C Monday night, coming close to Sarnia's March 4 record of -16.7 C set in 1950.
"When we're talking close to records, obviously it's because we haven't seen it that cold or that extreme for quite some time, or possibly ever," said Kimbell. "It's very unusual. The normal high for this time of year would be 4 C."
It will remain unseasonably cold through Wednesday and then gradually get warmer with a high of 4 C (39 F) Saturday and 6 C (43 F) Sunday.
The temperature will drop below seasonal again early next week before rebounding again.