Environment Canada and Ottawa Public Health have issued heat warnings this weekend, as daytime temperatures are expected to reach a high of 30 C with a humidex near 40 C Monday and Tuesday.
Environment Canada's advisory also covers Gatineau, Prescott-Russell and Cornwall-Morrisburg.
It says temperatures should slightly drop to the mid 20s by Tuesday, but it will still be quite humid.
There is also a severe thunderstorm watch for Ottawa, Prescott-Russell and west Quebec and a ban on open fires from Ottawa Fire Services.
The public, especially those who are susceptible to heat stress like seniors and young children, should drink plenty of water and limit physical outdoor activity.
7 tips to stay cool
Officials say extreme heat could cause dehydration, heat exhaustion, heat stroke and even death.
Here are some tips they shared to stay cool:
1. Drinking lots of fluids is key to avoiding dehydration. Drink lots of cool water even before you feel thirsty.
2. Find some place air conditioned to hang out, like a shopping centre, library, community centre, swimming facility or grocery store. Many cities offer cooling centres during periods of extreme heat.
3. Be on guard for symptoms of heat-related illnesses which include heat stroke, heat exhaustion, heat rash and heat cramps. Symptoms may range from dizziness or fainting, nausea or vomiting, headache, rapid breathing and heartbeat or extreme thirst. If those symptoms develop, find a cool environment and try to drink two or three glasses of cool water.
Someone who has a high body temperature and is either unconscious, confused or has stopped sweating may be suffering from heatstroke and 911 should be called immediately. While waiting for help, the person needs to be cooled down right away.
4. Avoid sun exposure by shading yourself by wearing a wide-brimmed breathable hat or using an umbrella. Wear loose-fitting, light-coloured clothing made from breathable fabric. Also, the shade from trees can be as much as 5°C cooler than the surrounding area.
5. People are warned to not use a fan in a closed room without windows or doors open to the outside. Fans do not cool air, just move it around and cool you down by evaporating your sweat. Also, don't use a fan to blow extremely hot air on yourself. This can cause heat exhaustion to happen faster. Use your fan in or next to a window.
6. Remember, the inside temperature of a vehicle can climb to more than 50 C when the outside temperature is 23 C. So never leave people or pets inside a parked vehicle during high temperatures.
7. Avoid intense or moderately intense physical activity especially between 11 a.m and 4 p.m.