Why southern Ontario is experiencing a heatwave and when it will break

Temperatures are soaring around Ontario. Photo from Canadian Press.

It’s been a scorcher over the past few days in southern Ontario, but relief will thankfully soon be on the way in the form of a cold front.

“It’s the summer we never had – that came in September,” joked Brett Anderson, a senior meteorologist with AccuWeather.

With temperatures in the mid 30s and almost as high as 40, it’s certainly felt like the peak of summer. So why are we experiencing this kind of heat in late September?

An unusually strong pressure system that’s been anchored across the Great Lakes Region has basically created a big bubble, explained Anderson.

“It forces the jet stream, which normally delivers the cool air from the north, to go way up north across north eastern Canada,” he said. “That keeps most of the cool air across western Canada so its deflecting all the cold fronts that we usually see this time of year to the west at this point.”

As for the next few days, the weather is going to make a dramatic shift.

“Things are going to change. We’re going to finally get a cold front on Wednesday and the heat wave will be a memory by Thursday,” said Anderson. “We’ll be looking at a high of about 29 in Toronto on Wednesday, so way above normal, probably even a record, but by Thursday it’ll be about 20 degrees, which is near normal for this time of year.”

But the normal weather isn’t going to last long – Anderson predicts temperatures will bounce back up again.

“I would not be surprised if at some point next week we see temperatures back into the mid twenties. I don’t see any sustained chilly weather over the next two weeks anywhere across southern Ontario,” he said.

As for what this all means for winter in southern Ontario, Anderson said it’s too early to say.

“We haven’t come up with a forecast yet, but right now it looks like we’re going to be dealing with at least a weak La Niña this winter,” he said. “Typically, when we have a weak La Niña it usually means – again, this it not a forecast – but what it usually means is that the cold air tends to concentrate across western Canada into the Prairies, and if that’s the case, it usually leads to milder conditions across eastern Canada.”