Heat dome will bring scorching temperatures to Toronto starting on Monday. Here is why it is likely to get worse

It could feel like 41 in the Toronto area on Monday and a senior climatologist with Environment Canada is warning that the conditions will likely become even more unbearable later this week due to a weather phenomenon known as a “heat dome.”

Dave Phillips made the comment to CP24 as he discussed a heat wave that could see temperatures top 30 C for the next four days.

The high temperatures will also be accompanied by significant humidex values that could make it feel like 40 or 41 through Thursday in the GTA. Residents will get a bit of a relief on Friday but barely. It will still reach a daytime high of 27 C and feel like 35 with the humidity.

“We are under the dome, the heat dome and it is like putting the Rogers Centre over a good chunk of North America from Atlanta, Georgia to Atlantic Canada and air doesn’t circulate, it just stays there,” Phillips warned. “In fact what happens under the dome is the air just squeezes down and all those little air molecules jiggle and create more heat and the heat can’t go anywhere. It stays put and it gets hotter as you get closer to the surface.” 

• For a closer look at the sweltering conditions and CP24's latest forecast follow this link.

Environment and Climate Change Canada issued a heat warning Sunday which remains in effect for all of southern and central Ontario and parts of northern Ontario.

The agency warned that daytime highs will be between 30 to 35 degrees for most of the week, with overnight lows of 20 to 23 degrees that could still feel between 26 and 30 with the humidity.

Speaking with CP24, Phillips said that the overnight conditions in particular are concerning because they will mean that there will effectively be “no escape” from the sweltering conditions for vulnerable residents.

He also warned that the conditions are likely to become more challenging as the week goes on as a result of the heat dome phenomenon, which won’t allow hot air to escape.

“The heat dome is always worse at the end than the beginning. At the beginning the body is fairly resilient. We can handle one day, even people who have health related issues. But towards the end the body wears down. You can’t take it morning, noon and night and then you add to that the humidity and the air pollution. You can’t breathe.”

City opens some pools early, extends hours

Ahead of the heat wave, the City of Toronto has announced plans to open 10 outdoor pools and 10 wading pools ahead of schedule. 

The city has also anouced that it is extending the operating hours at those 10 pools.

From Monday until Thursday, Heron Park Community Centre, Kiwanis Outdoor Pool, Pine Point Park Outdoor Pool, Riverdale Park East, and West Mall Outdoor Pool will be open, weather permitting, until 9 p.m.

Alex Duff Memorial Pool, McGregor Park, North Toronto Memorial Community Centre, Parkway Forest Outdoor Pool, and Sunnyside Gus Ryder Outdoor Pool will be open, weather permitting, until 10 p.m. on Monday night.  

Starting on Tuesday until Thursday, these locations will be open until 11:45 p.m., weather permitting, the city said.

All other City of Toronto pools are scheduled to open for the season on June 28.

Splash pads have also opened for the season and are operational daily from 9 a.m. to 9 p.m. 

Librairies and community centres are also places where people can go for shelter from the heat.

In its warning, Environment Canada cautioned that extreme heat poses a health risk, especially for older adults, infants, young children, those who are pregnant, people with physical and or mental illnesses, and those with mobility issues.

People are being advised to reduce or avoid strenuous physical activity outdoors where possible, and to stay hydrated.

People are also being reminded not to leave anyone, particularly children, or pets, inside of a park vehicle.

“Kids have a lot of surface area for their size so they may actually lose a lot of fluid and a lot of electrolytes when they are being active and even just hanging out in a warm classroom setting. They may not sweat as much as older people as well and sweating helps us regulate our body temperature.” Dr. Dina Kulik, a pediatrician and founder of Kidcrew Medical, told CP24 on Monday afternoon. “So we always want to make sure your kids are drinking lots even if they are not saying they are thirsty. Do force it on your kids even if they aren’t asking for it.”

Kulik said that there is always an uptick in the number of children visiting emergency rooms with heat-related illnesses during heat waves. She said that the best way to keep kids safe is to “touch base” with them off and make sure that they are getting fluids and breaks from the sun.

“Are they not as interactive with you bas before? Are they confused? Do they have a headache or dizziness?” she said. 

The sweltering 30-plus temperatures are expected to last through Friday. Highs are expected to return to the mid-20s over the weekend.

With the hot and humid conditions, thunderstorms are also a possibility.