Historic heatwaves have killed around 486 people in British Columbia over the past five days. Millions of people are still suffering as heatwaves threaten areas of Canada and the United States.
The worst-hit areas include the Pacific coast province of British Columbia in Canada and Washington, Oregon, Idaho, Montana, and California in The United States.
On Tuesday 29 June, the town of Lytton in British Columbia recorded 49.6 degrees Celsius, which is Canada's all-time record high by 3 degrees. Temperatures hit 46.6C in Portland, Oregon, and 42.2C in Seattle, Washington, the highest levels since record-keeping began in the 1940s, says the National Weather Service.
At least 63 people have died in Oregon over the past few days. Forty-five of those deaths were recorded in Multnomah County.
The US National Weather Service has warned that the heatwaves caused by the 'heat dome' could last until Thursday.
What is a heat dome?
A combination of atmospheric pressure and rising sea temperatures have contributed to this life-threatening phenomenon. Temperatures at the ground level rise as high pressure in the atmosphere act like a block in the atmosphere and the rising temperature get trapped inside. Weather scientists have called this phenomenon as heat dome. It's essentially a mountain of warm air built into a very wavy jet stream, with extreme undulations.
A strong change in the ocean temperatures from west to east in the tropical Pacific Ocean during the preceding winter has led to this heatwave, according to a study by a team of scientists sponsored by the National Oceanic and Atmospheric Administration (NOAA).
Since the pressure system has been formed in the shape of the Greek letter Omega, the specific type of block is called an Omega block.
The high-pressure dome appears to be stationary and isn't easy to move around. However, it leads to a heatwave when strong winds move the heat dome around.
