After three back-to-back days of insufferable heat, Montreal has broken the monthly maximum temperature record for June.

The province has been gripped by an intense heat wave since Sunday.

On Tuesday, temperatures in Montreal hit 35.1°C, edging past the previous record of 35.0°C set on June 30, 1964.

On Monday, Dorval saw a high of 34.9°C, while Gatineau reached a scorching 36.6°C, breaking the 1988 record.

While the heat wave is expected to subside, the summer 2025 weather forecast says there will be more intense humidity and heat in the future.

What is the hottest it’s ever been in Montreal?

The warmest day ever in Montreal occurred during the historic heatwave of 1975, with a temperature of 37.6C (99.6F) on August 1, 1975.

Photograph: Shutterstock / Marc Bruxelle

How to cool off in a heat wave?

According to their website, the City of Montreal suggests taking the following precautions during a heat wave in order to reduce health risks:

Drink lots of water before you feel thirsty

Spend a few hours a day in an air-conditioned or cool location

Take a cool shower or bath or cool your skin with a damp cloth

Reduce your physical efforts

Wear light-couloured clothing

Don’t drink alcoholic beverages, beverages with a high caffeine content or high sugary content in moderation, as they dehydrate you

The opening hours of many public places could be extended during a heat wave, so be sure to look up the site’s opening hours before you make your way there.

Find an indoor or outdoor facility near you: neighbourhood parks, nature parks and large parks; swimming pools, wading pools, beaches, mist stations and play fountains; libraries and air-conditioned places

Photograph: Colin Woods

If you don’t have access to air conditioning close to home, or if you have difficulty getting around, here are a few tips for your home:

Avoid using heat-generating appliances (stove, oven, dryer, TV, lights, etc.)

Close windows, curtains, blinds and doors during the day. Air your home out in the evening, at night or early in the morning

Circulate air with portable or ceiling fans

Use the technique of placing a frozen water bottle in front of a fan to diffuse cooler air

During a heat wave, your health could degrade rapidly. Call Info-Santé at 811 or talk to a health care professional if you have these symptoms:

Exhaustion (fatigue)

Dehydration (dry mouth)

Redness or rash on the skin

Headaches

Dizziness (lightheadedness)

Confusion

If you have these symptoms and are also feverish, you may be experiencing heat stroke. This is a medical emergency. Call 911 to get help quickly.

The following people are at higher during a heat wave:

People who are 65 or older

People living with chronic, cardiovascular, respiratory, kidney or neurological conditions or diabetes

People living with mental health conditions or with alcohol or drug addiction

People who work outdoors or near a heat source

Children younger than 4 years old

During a heat wave, take a few minutes, on a regular basis, to look out for the well-being of your loved ones and the people in your neighbourhood who are more isolated

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A heat wave over Ontario and Quebec delivered a parting punch of scorching temperatures on Tuesday, as hydro crews worked to restore power to tens of thousands of customers in areas hit by forceful thunderstorms.

Across southern Ontario and Quebec, temperatures hit the low to mid 30s. The humidity made it feel closer to the low 40s.

The heat’s grip was expected to loosen by Tuesday evening or into the overnight, but daytime temperatures throughout the week were still expected to be in the high 20s with a “a fair amount of humidity,” Environment Canada meteorologist Steven Flisfeder said.

Any relief was expected to be short lived with more 30-degree days in the forecast starting Friday for parts of southwestern Ontario.

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“It may seem like a double slap in the face to some people, especially those who are more susceptible” to heat, said Flisfeder.

Heat warnings were in place Tuesday from Windsor through to Quebec City after days of record-breaking temperatures.

Toronto, Ottawa and Montreal were among the cities to set new June 23 daily temperature records, said Flisfeder.

“It’s almost too many to list off,” he said.

As the high-pressure system moved east, heat warnings were extended on Tuesday to the southern part of Nova Scotia, where they were expected to remain in place through Wednesday.

Meanwhile, severe thunderstorms rolled through areas along the edges of the heat-trapping high-pressure system. Just under 32,000 Hydro-Québec customers, mostly around Québec City, remained without power as of 4:30 p.m. on Tuesday in the aftermath of thunderstorms, down from a high of around 125,000 customers, officials said.

In parts of Ontario, More Hydro One customers lost power Tuesday, adding to those who were still waiting to have the lights turned on again after weekend storms. Hydro One reported more than 4,000 customers were without power as of 4:30 p.m., up from earlier in the day.

Open this photo in gallery: Workers try to stay hydrated in Toronto. The city, along with Ottawa and Montreal, set a new daily temperature record for June 23.Sammy Kogan/The Globe and Mail

The extreme heat and power-disrupting thunderstorms can make for a dangerous combination, said Flisfeder.

“We tend to tell people to get inside where there’s AC available. Having no power, that obviously reduces the availability of that cooling and refuge from the heat and dangerous conditions,” he said.

“It certainly is a concern.”

Forecasters warn extreme heat this early in the season can be particularly alarming since people are not acclimatized to the high heat and humidex values, which are well above normal.

The temperatures were about 10 degrees warmer than normal for this time of year.

“It is very unseasonably warm, and the humidity just makes it even more uncomfortable,” said Flisfeder.

Ontario heat wave prompts concerns about students, educators sweltering in schools

Studies indicate that climate change, driven by the burning of fossil fuels, is increasing the length and intensity of Canadian heat waves.

Toronto’s transit agency said it had implemented a few speed reduction measures along above-ground areas of its subway lines to avoid heat-related track issues. On the streetcar network, some issues had been reported with overheard wires due to excessive heat, but disruptions were temporary, said a spokesperson with the Toronto Transit Commission.