Environment Canada has issued a heat warning Wednesday afternoon that covers Ottawa, Gatineau, Que., and communities as far south as Gananoque, as far west as the Perth area and as far east as the Quebec border.
The dangerous heat is expected to hit Thursday and last through Friday and potentially into the weekend.
People could see daytime temperatures reach 30 or 32 C, with humidex values near 40, Environment Canada said. Nighttime lows could stay above 20 C.
Extreme heat can pose significant health risks to everyone, but certain groups are particularly vulnerable. These include older adults, infants and young children, pregnant people and those with physical or mental health conditions.
Ottawa Public Health offers an interactive map of places to stay cool throughout the city, including pools, libraries, splash pads and community centres, plus fountains. Other health authorities and municipalities have shared similar maps.
Everyone is being asked to avoid exercising during peak heat times, staying inside where possible — especially in spaces that are being cooled — and drinking plenty of fluids.
Thunderstorm warning no longer in effect
The agency also had severe thunderstorm warnings Wednesday afternoon covering a strip of land around Gatineau and as far north as Maniwaki.
As of 7:30 p.m. on Wednesday, these warnings were no longer in effect.
Severe thunderstorm watches are issued when conditions are likely to produce those storms. They are upgraded to warnings when one of those weather elements becomes more certain.