An Environment Canada meteorologist warns records will likely fall Friday night when the night-time low falls below 0 C.
"We're talking about possibly records being broken Friday night," said Gerald Cheng.
Usually, Southwestern Ontario can expect a night-time low of 7 C or 8 C at the beginning of May. During the day, Southwestern Ontario typically reaches 20 C, but over the past two days, temperatures have been almost 10 C cooler.
Cheng explained you can blame it on the jet stream over Ontario.
"We do see the jet stream really sinking south," he said. "It's that cold air from the Arctic is able to push down to Southwestern Ontario."
And do not expect relief any time soon. He said it could take more than a week for the temperatures to recover.
"We are on our way down with the bottom of the valley this weekend," Cheng said. "Next week, things will gradually rise, but still not seasonal until the next weekend for things to get back closer to normal."
To reach a record, the temperature in Windsor-Essex will have to fall to -1.7 C, -4 C in London, and -1.3 C in Sarnia.
