Sweltering heat descends on northeastern Ontario as warnings cover most of region

Environment Canada issued orange and yellow heat warnings across northeastern Ontario on Monday, with humidex values forecasted to reach up to 45 and temperatures peaking near 37 C on Tuesday.

A prolonged heat event began Monday across much of northeastern Ontario, with Environment Canada issuing a mix of orange and yellow warnings spanning dozens of communities from the shores of Lake Superior to the Quebec border. Forecasters say the event will bring maximum temperatures ranging from 29 to 37 degrees Celsius, depending on location, with humidex values making it feel as hot as 45 in some areas. The warnings are separated by severity, with orange-level alerts carrying a high impact level for several communities while yellow warnings indicate moderate risk.

LEARN MORE: What’s with the colour-coded weather alerts? Here’s what you need to know Orange warnings Orange warnings are in effect for Timmins, Cochrane, Chapleau, Dubreuilville, Elliot Lake, Hearst, Kapuskasing, Missinaibi Lake, Ranger Lake, Smooth Rock Falls, Temagami, Temiskaming Shores and White River. For these areas, Environment Canada forecasts maximum temperatures of 32 to 37 degrees, with minimum temperatures of 19 to 23 degrees.

Humidex values are expected to range from 36 to 42. The heat event is expected continuing through Tuesday evening for most of these communities. “Hot and humid air can also bring deteriorating air quality and can result in the Air Quality Health Index approaching the high-risk category,” the weather agency said in its alerts.

Yellow warnings Yellow warnings cover a larger geographic area, including Greater Sudbury, North Bay, Parry Sound, Sault Ste. Marie, Batchawana Bay, Blind River, Espanola, French River, Killarney, Mattawa, Montreal River Harbour, Moosonee, Powassan, Rosseau, Searchmont, St. Joseph Island, Thessalon, West Nipissing, and Killbear Park. These areas are seeing maximum temperatures of 29 to 37 degrees, with minimum temperatures of 18 to 24 degrees, depending on the specific location.

Humidex values of 38 to 45 are expected. The yellow warnings began Monday and are set to end either Wednesday evening or Thursday evening, though the event for Sault Ste. Marie and Searchmont areas is expected to end Tuesday evening.

“Cooler temperatures are expected for locations near to Lake Superior,” Environment Canada said in the alerts for the Sault Ste. Marie and Searchmont regions. Tuesday will mark the peak of this heat event, with maximum temperatures near 37 degrees expected for some areas.

Health risks, safety measures Environment Canada has urged residents to take action to protect themselves and others, saying that extreme heat can affect everyone’s health. “Determine if you or others around you are at greater risk of heat illness. Check on older adults, those living alone and other at-risk people in person or on the phone multiple times a day,” the weather agency said in its alerts.

Officials also advised residents to watch for early signs of heat exhaustion in themselves and others, which may include headache, nausea, dizziness, thirst, dark urine and intense fatigue. Environment Canada said heat stroke is a medical emergency and residents should call 911 or their emergency health provider if they or someone around them is showing signs of heat stroke, which can include red and hot skin, dizziness, nausea, confusion and change in consciousness. “While you wait for medical attention, try to cool the person by moving them to a cool place, removing extra clothing, applying cold water or ice packs around the body,” said officials.

Download the CTV News app now Sign up for breaking news alerts Get daily newsletters with the top local stories emailed to your inbox Practical steps for staying cool Environment Canada also recommended a range of measures to help residents cope with the heat. “Drink water often and before you feel thirsty to replace fluids,” the alerts said. Residents are encouraged to close blinds or shades and open windows if outside is cooler than inside or turn on air conditioning, use a fan, or move to a cooler area of their living space.

If a living space is too hot, the agency suggests moving to a cool public space such as a cooling centre, community centre, library or shaded park. LEARN MORE: Residents seek cooling options as northern Ontario faces heatwave Officials said people should plan and schedule outdoor activities during the coolest parts of the day and limit direct exposure to the sun and heat. Lightweight, light-coloured, loose-fitting clothing and a wide-brimmed hat are also recommended.

LEARN MORE: Outdoor workers find ways to cope during heatwave “Never leave people, especially children, or pets inside a parked vehicle. Check the vehicle before locking to make sure no one is left behind,” said Environment Canada.

For areas experiencing both extreme heat and wildfire smoke, the agency advises prioritizing keeping cool. Hourly and 7-day forecast on our CTVNorthernOntario.ca weather hub Ongoing monitoring Environment Canada urges residents to continue monitoring the agency’s alerts and forecasts throughout the heat event. Report severe weather by email to ONstorm@ec.gc.ca or on X using the hashtag #ONStorm .