Parts of southern Ontario and Quebec will feel like a sauna much of this week with temperatures exceeding 30 C, and high humidity expected to make it feel even hotter.

Environment Canada issued a high heat and humidity warning Monday for a large swath of Quebec stretching from Pontiac to the Eastern Townships, including Montreal.

The area will see humidex values of 40 or higher and temperatures exceeding 30 C, the weather agency said.

The temperature is expected to reach 32 C in Montreal and 31 C in Quebec City on Monday. The heat will start to subside late in the week, when Environment Canada forecasts the temperature in the region will drop to the mid-20s.

“A warm and humid air mass covering southern Quebec for a few days is producing an uncomfortable heat wave,” Environment Canada said in an alert Monday afternoon.

Seniors, people with chronic diseases, and children under the age of 4 are most vulnerable to the heat, the weather agency warned.

Montreal emergency room physician Dr. Mitch Shulman urged residents to take it easy and limit physical activity.

“You can’t function in the high heat and especially in the high humidity, your body can’t keep you cool, so avoid the peak times of the day when the sun is at its strongest, try and limit your activities, if you don’t, you risk being seen by me in the emergency room,” he said Sunday.

Ontarians from Windsor to Ottawa will also be sweating it out with temperatures in the 30s and high humidex values in the 40s predicted for much of the week.

Ottawa Public Health issued a heat warning for the capital as the forecast predicted the mercury would hit 34 C on Monday and Tuesday.

Luckily the city’s five public beaches are open for swimming, and a number of public cooling centres have been opened.

The city of Toronto also issued a heat alert, with the temperature expected to climb to 33 C Monday afternoon with a UV index of 10. Tuesday and Wednesday will bring little relief, as the temperature is expected to hover around 33 C.

Lifeguards at the city’s public pools said they’re ready for the increase in the number of swimmers as the week wears on.

In Windsor, residents can expect a high of 33 C Monday as well as a 60 per cent chance of a thunderstorm.

The sticky weather conditions are expected until the weekend, when the temperature is predicted to drop to the mid-20s.

Residents in the affected areas are encouraged to do the following to keep cool:

  • Drink lots of water even before you feel thirsty
  • Go to indoor air-conditioned places, including shopping malls, community centres and local libraries
  • Limit physical activity
  • Check in on elderly family members and neighbours
  • Never leave seniors, children or pets in unattended cars
  • Seek shady areas or use an umbrella when outdoors
  • Take cool showers or baths, or use wet towels to cool down
  • Wear loose, light-coloured clothing and wide-brimmed hats when outdoors
  • Reschedule outdoor activities to the cooler evening hours