US, Canada Heatwave: What is the Cause? When Will It Ebb?

Hundreds of deaths across the United States and Canada have been linked to this heatwave.

3 min read

Video Producer: Shohini Bose
Video Editor: Vivek Gupta

Seattle, Portland, and a number of American cities are believed to have broken all-time heat records, with temperatures in some places recording above 115 degrees Fahrenheit (46 degrees Celsius). Meanwhile, Canada is witnessing a spate of horrific wildfires with British Columbia Wildfire Service listing 99 active fires and 78 being reported just within the last two days.

Hundreds of deaths across the United States and Canada have been linked to this heatwave.

Sharing a map with heat spots (recorded through 2020), the National Weather Service (NWS) Portland tweeted: “That is not a lot of red and yellow dots in our area. This just shows how uncommon these temperatures are in our neck of the woods.”

Meanwhile, multiple pyrocumulonimbus plumes have been reported amid wildfires in British Columbia.

Pyrocumulonimbus plumes have been described, in Summerland Review, as “large, billowing clouds that can surge over 50,000 feet high during extreme wildfires, essentially creating their own storms by generating lightning.”

But what is a heatwave? What is causing it? And when will it end?


What is a Heatwave?

A period of excessively hot weather, which may be accompanied by humidity, can be generally defined as a heatwave. Countries that are not prone to hot climatic conditions may be less equipped to handle a heatwave.

As per the National Weather Service, temperatures ought to be above the historical average in the region for two or more days before the spell is dubbed a “heatwave”. But the definition can vary by region.

An onset of heatwave can cause deaths from hyperthermia, crop failures, and widespread power outages.

What is Causing the Heatwave in the US and Canada?

When high pressure in the atmosphere intensifies over a specific region over several days or weeks, it leads to the formation of a heatwave.

The US/Canada heat wave has been caused by a dome of high pressure over the Northwest and worsened by human-induced climate change, reported AP, citing meteorologists. Climate change, as per the meteorologists, can intensify extreme weather events, and make the possibility of their occurrence more likely.

As per AFP, the phenomenon causing this heatwave, which is dubbed “one of the most extreme heatwaves that we have seen on Earth”, is called a “heat dome”.


What is a Heat Dome?

As per AFP, a heat dome is when hot air is trapped by high pressure fronts, and as it is pushed back to the ground, it heats up even more.

“It’s sort of like a bicycle pump,” Philip Mote, professor of atmospheric science at Oregon State University, told AFP.

“If you compress air into a bike tire, it warms the air.”

Further, the condition keeps clouds from forming, thereby allowing more of the sun’s radiation to hit the ground.

What is the Climate Change Connection?

Zeke Hausfather, a climate expert at the Breakthrough Institute, told AFP: “A world without climate change would have still had a heatwave in the Pacific Northwest. It just would have been not quite as record-setting.”

Dubbing climate “like steroids for the weather,” Hausfather said:

“If a baseball player or Olympic athlete is taking steroids, they’re still going to perform better some days and worse some days, but on average, their performance is going to go up. And so climate is doing something similar to the weather. That makes it more likely to experience these sort of extremes.”

Daniel Swain, a climate expert at UCLA, also iterated that “it is very possible that climate change increased this heat wave to an even greater degree”, observing that the drought that the region has been witnessing for weeks may have bolstered the heat dome because the energy of the sun’s rays is no longer being used to evaporate water, so instead it warms the atmosphere more, reported AFP.

Pointing out that, that “attribution studies” will be carried out to arrive at the exact causes of this event, Karin Bumbaco, a climatologist at the University of Washington, told AFP:

“(But) I think it’s safe to say that there’s at least some components of global climate change that contributed to this event”.

Hausfather added, “We’re stuck with the warming... And so we need to be prepared for these sorts of events to be more frequent.”

When Will This Heatwave Ebb?

Forecasters have, as per The Indian Express, pointed out that the temperatures will be unreasonably hot next week as well in the Pacific Northwest.

Clinton Rockey, a meteorologist with the National Weather Service in Portland, has said that temperatures have somewhat moderated in Portland, but are expected to reach the mid-80s later in the week and will remain 10 to 20 degrees above average at least until next Tuesday.

(With inputs from AP, AFP, and The Indian Express.)

(At The Quint, we are answerable only to our audience. Play an active role in shaping our journalism by becoming a member. Because the truth is worth it.)

Speaking truth to power requires allies like you.
Become a Quint Insider

or more


3 months
12 months
12 months
Check Insider Benefits
Stay Updated

Subscribe To Our Daily Newsletter And Get News Delivered Straight To Your Inbox.

Join over 120,000 subscribers!