The extreme heat that is baking parts of the northeast United States has also settled over Toronto and parts of eastern Canada for the third day in a row, pushing many Canadians indoors to seek air-conditioned relief.

The heat led to the temporary closings of some public pools because it was too hot for lifeguards to work, according to local regulations, much to the consternation of many residents.

Temperatures in Toronto on Monday reached 36 degrees Celsius, or 97 degrees Fahrenheit, making it the city’s hottest day since July 13, 2016, according to Environment Canada, which runs a federal meteorological service.

The stifling heat continued into Tuesday, with Toronto recording an afternoon temperature of nearly 36 degrees Celsius, or 96 degrees Fahrenheit, with high humidity readings making conditions even more sticky and unpleasant.

“The ability for the body to regulate its temperature is far more difficult when we have those high humidity, muggy days,” said Steven Flisfeder, a meteorologist at Environment Canada.

The weather prompted health warnings from Toronto officials who advised people to remain in cool spaces, drink plenty of water and recognize the signs of heat exhaustion, which include nausea and extreme fatigue.

Some easing of the heat should come on Wednesday, when temperatures in Toronto and the surrounding areas are expected to dip to levels that are more typical of late June, forecasters said.

The sporadic closing of some public pools in Toronto provoked an outcry from people who had looked forward to a cool dip. The shutdowns were caused by labor safety regulations that limit working in extreme heat, said Olivia Chow, the city’s mayor, who apologized for the action.

“This cannot happen again,” Ms. Chow said. “When it’s hot outside, residents need to be able to get out to the pools and cool down.”

To avoid a repeat, the city is looking at increasing the number of lifeguards and building more spaces for them to take shade, Ms. Chow said.

The Toronto District School Board sent an advisory to parents asking them to prepare students for “uncomfortable conditions.” The school year ends on Friday. The district, Canada’s largest, runs 579 schools, and of those, only 177, or about 30 percent, have air conditioning, according to the school board.

About two-thirds of Canadian homes have air conditioning, according to the national census agency. In the United States, about 90 percent of homes are air-conditioned.

Ottawa, Montreal and other cities across the southern regions of Ontario and Quebec were experiencing similar heat and humidity levels.