THE CANADIAN PRESS -- TORONTO - A blanket of stifling heat, oppressively still and sticky with humidity, has settled over large swaths of the country -- and it's here for the long haul.
Canadians who feel like they are being roasted in an oven, stewing in their own juices, are not that far off.
A heat dome, a hot, unmoving high-pressure area, is hovering over central parts of Canada, pushing the jet stream well to the north, and keeping cooler or wetter weather out, said Environment Canada senior climatologist Dave Phillips.
"It's like a heat pump and it just sluggishly sits there and like an unwanted house guest, it just won't move," he said.
The dome is hovering over much of the United States as well. It spread up to western Canada over the weekend, sending sizzling temperatures to the Prairies. Winnipeg was sweltering under a high of 34.4 C on Tuesday and Regina baked at 31.9 C.
As the dome settles a bit further east, Environment Canada is predicting the mercury will hit 37 C Thursday in Toronto. Further south in Windsor, Ont., it's expected to go up to a scorching 39 C.
The heat dome phenomenon is known to happen every few summers, said Marie-Eve Giguere, a warning preparedness meteorologist with Environment Canada. The dome works to trap heat, she said.
"Every day it gets hotter and hotter," Giguere said. "It gets heat from the sun and this sort of hot dome of air is getting hotter and hotter and this is what's creating these high temperatures."
Another kind of dome is a concern in Toronto. The Blue Jays decided to close retractable roof at Rogers Centre during the heat of the day on Thursday afternoon when they play the Seattle Mariners.
There is some slight relief ahead. But only slight.
"Come Friday, it's going to cool off," Phillips said without a trace of sarcasm. "In the Toronto area the high is only going to be 32 or 31."
Just be glad it's not 1937 -- that's when the hottest temperature ever was recorded in Canada, with a high of 45 C in Midale and Yellow Grass, Sask.
Still, temperatures in the high 30s are expected to feel more like 48 C.
Municipalities across Ontario such as Ottawa, the Niagara region, Waterloo and Cornwall are issuing various heat alerts and advisories, which allow for city cooling centres to operate.
The Windsor-Essex Health Unit has issued a level 2 heat alert, which is put in place when the forecast predicts four or more days with a humidex value reaching 40.
In Toronto, the medical officer of health upgraded a heat alert to an extreme heat alert and hours have been extended at some city pools.
During working hours, many sit comfortably in air conditioning, but not Marvin, who didn't want his last name used.
He works in a factory baking facility with five ovens.
"Imagine if it's hot outside, it's actually hotter inside," he said, joking that he thinks it would be cooler to actually crawl inside a home oven.
"If you turned on your oven for 250 degrees it's actually cooler in there."
An eight-hour shift passes slowly in such a sauna-like environment, but Marvin said he makes it through the day by drinking lots of water.
"If you don't pass out in-between, then you'll be OK," he said.
Annabelle Villa-Real manages a bagel shop in Toronto, where she has been working for almost 16 years, and credits coming from the Philippines for being able to work among three ovens and no air conditioning.
"All the time people say, 'How do you survive, Annabelle?'" she said. "Think positive."
Villa-Real and her staff take plenty of breaks, drink cold water and snack on Popsicles, have ice at the ready, as well as towels and extra shirts.
"We're used to it and it's no big deal to us," she said. "The weather? Aw, go to the bakery. We're the last man standing."
One of the most remarkable features of this prolonged blast of heat is that it's not cooling off much even overnight, Phillips said/
Minimum temperatures should be about 17 C, but the Thursday minimum for Toronto is expected to be 25 C, and the same for Montreal on Friday. In Windsor, it may only go down to 26 C overnight Wednesday.
In heat waves in North America and Europe that have proved deadly, the common feature is that during the night the temperatures don't dip below 20 C.
"The body doesn't have a chance to rebuild itself and get ready for the next daily onslaught," Phillips said.
The 10-day forecast shows hotter-than-normal temperatures from eastern Alberta through to Prince Edward Island, and the long-term forecast for August sees temperatures above average from coast to coast, Phillips said.
"It may not be as 345 warm, but we can clearly see this thing is not going to go away and be replaced by some cold, Canadian air," he said. "It's likely to rebuild itself when it peters out."