Demands for electricity are hitting seasonal highs as temperatures continue to soar across Ontario and Quebec, yet warnings to conserve energy aren't being issued as they used to be.

Temperatures across southern Ontario and Quebec have been sitting in the low to mid 30s with humidex values in the 40s, and the extreme heat and humidity are expected to continue Thursday.

At Montreal's Trudeau airport, the temperature hit 32.2 C, breaking the June 20 record of 32 C, which was set in 1988. Toronto, which saw temperatures of 34.4 C at Pearson airport, tied — and possibly broke — its daily temperature record that was originally set in 1949 and matched in 1988.

In the past, such heat waves caused Ontario to struggle to meet the demand for electricity, which would sometimes result in brownouts or blackouts.

"The system was strained, we were relying on our neighbours to sell power to us so we had enough supply to meet the high demands associated with air conditioning," said Terry Young, an independent electricity system operator.

Emergency cooling centres have been opened in several areas affected by high temperatures. (John Rieti/CBC)

A warning about brownouts hasn't been issued since 2007, with experts crediting both conservation efforts and less demand because of the downturn in the economy.

In 2006, Ontario hit a record for electricity demand during an August heat wave. Two years later, the financial crisis hit, forcing many factories to close and businesses to downsize.

"There may even be some industrial users of electricity who, in exchange for a reduction in their electricity rates, may get the request to shut down for an hour or two," said Danny Harvey, a geography professor at the University of Toronto specializing on climate change and energy and environment.

"A few hours a year, and you see this avoids either the brownout or it avoids the need to build additional power generators."

Other factors include refurbished nuclear reactors and new gas power plants that pump more electricity into the system, as well as solar panel installations.

On Wednesday evening, Toronto Hydro's website did show some limited power outages in the city, with the largest in the west end.

"We're currently experiencing a number of localized power outages across the city due to warmer weather conditions," Toronto Hydro said on Twitter. Earlier in the day, the utility posted tips about conserving energy while running an air conditioner.

2nd day of extreme heat

Meanwhile, Environment Canada issued a humidity warning for Montreal and parts of Quebec. Health officials in Montreal warned people Wednesday to find ways to keep cool, as temperatures reached 32.2 C and felt like at least 40 with the humidity.

Beachgoers try to beat the heat. Records were broken in some communities in both Quebec and Ontario on Wednesday. (CBC)

CBC meteorologist Michelle Leslie said much of Ontario is experiencing a heat wave.

"A heat wave is designated when the temperature hits 32 degrees or higher for at least three consecutive days," Leslie said.

"The city of Toronto topped out at 33 C yesterday," Leslie said. But the temperature crept higher Wednesday, and was hovering at 34 C around 6 p.m., according to Environment Canada. The Pearson high was 34.4 C, but CBC meteorologist Michelle Leslie said that figure was later revised unofficially to 34.6 C. If that's the official temperature, it would be a record-breaking daily temperature.

Temperatures across southern Ontario are forecast to remain in the low 30s with humidex readings in the 40s. On Wednesday, Toronto issued an extreme heat alert as temperatures were expected to reach a high of 35 C with added humidity making it feel more like 42.

The city of Hamilton also issued a heat warning on this first day of summer, expecting the humidex to be at about 40 for the next few days, with increasing smog causing a forecast of moderate air quality for the area.

Ottawa's temperatures were also expected to be in the mid 30s with humidex values above 40.

Cold front moving in

Leslie said Ontario should experience some relief by the end of the work week.

"A cold front moving into the lower Great Lakes for Thursday has indicated signs of weakening but should still be strong enough to trigger off thunderstorms later tomorrow and with the arrival of the front we should see a reduction in both heat and humidity," she said.

Leslie said there are many reasons why we are seeing such extreme heat before we enter the depths of summer.

"This past winter we saw well below average snowfall," she said. "Without enough snowfall — which equals evaporated cooling — we weren't able to freeze the land like we would in a typical winter and we didn't freeze Lake Ontario."

“We've already seen Lake Ontario's water temperatures above average,” she said. “Last week the lake temperature was around 17 C. Normally for mid-June it's closer to 10 C to12 C.”

Health officials are suggesting that people — especially the elderly and those with chronic illnesses — stay inside with air conditioning or seek the shade, as well as to limit physical activity and drink plenty of water.