Wildfires and tornadoes have a tangled relationship. Ontario researchers work to learn why

As another wildfire season gets underway in Canada, researchers with the Northern Tornadoes Project (NTP) at Western University have found a curious link between wildfires and tornadoes.

"One thing that we've noticed over the last few years is that when we have a really big fire year like last year, we tend to get less tornadoes," said David Sills, executive director of the NTP.

According to data from the London, Ont., university, Canada experienced a record-breaking 129 tornadoes in 2022. In 2023, amid the worst wildfire season this country has ever seen, there were just 86 twisters.

It's an unexpected parallel, one Sills said researchers have yet to fully understand. 

There are theories, though. 

"We get a lot more forest fire smoke that blows across the country when we get these big fire years," Sills said, "and having that smoke up there really cuts down on the amount of sunlight getting down to the ground and heating the ground, and providing instability for thunderstorms."

Last year, Canada saw some 18 million hectares of its vast forests go up in smoke, resulting in eight deaths and tens of thousands of people fleeing their homes. As the fires burned, blankets of smoke drifted across the continent, smothering Canadian and U.S. cities in an acrid fog so thick that it rolled back decades of air-quality gains.

That continent-spanning veil of wood smoke, Sills said, seems to have a diminishing effect on the size and power of thunderstorms. 

"We saw that last year. There were the same number of storms as usual, but their intensity was notably less. If that's the case, the chance of getting a tornado with a less intense storm is obviously less as well.

"So it might be an explanation for why we're getting less tornadoes when we think there's more fire going on."

Connecting the dots between particularly intense wildfire seasons and how it affects weather across the continent might take some time, especially when researchers are noticing historical tornado patterns are shifting. 

The NTP recently created an online portal on 40 years worth of scientifically collected information on tornadoes from 1980 to 2020, giving anyone with internet access an unprecedented look at Canada's extreme weather. 

"I think it's incredibly useful for scientists such as myself," said Geoff Coulson, a warning preparedness meteorologist with Environment Canada. 

"The database contains lots of information about not only where tornadoes have occurred over the last number of decades, but the ratings, how long they've been, the width of the damage. ... lots of very useful information for people who want to dig around and learn more about the tornado risk in various parts of Canada."