Final push of extreme heat and humidity for Ontario and Quebec

The end of the extended period of heat in Central Canada is beginning to appear on the horizon as temperatures will peak on Thursday, before falling to more seasonal levels on Friday.

The mercury has soared to the 30s in Ontario and Quebec, with humidex levels stretching into the 40s for many locales. Hot and humid air brought deteriorating air quality to numerous communities earlier this week, and resulted in the air quality health index (AQHI) getting near the high-risk category.

DON’T MISS: Why extreme heat is one of the world’s deadliest weather disasters

Watch out for heat-related impacts, such as heat exhaustion and/or heat stroke. Remember to drink plenty of water. Avoid strenuous work outdoors.

The heat and humidity, which will finally ease on Friday, has been and will fuel another thunderstorm risk on Thursday, so people will need to be weather-aware.

Major heat builds over the region

This week’s heat wave is likely break records across Ontario and Quebec as a strong ridge of high pressure builds over the eastern U.S. and the Great Lakes.

Air sinks beneath a strong ridge, warming up as it descends toward the surface. Hot, muggy winds blowing straight from the Gulf of Mexico will add tropical humidity to the mix.

ON QC humidex forecast Thurs
ON QC humidex forecast Thurs

DON'T MISS: This simple trick may save many kids' lives during a heat wave

Between the ridge and the humidity combined, we're in for a days-long stretch of hot daytime highs and little to no relief from the stuffy air at night.

The heat arrived in earnest Tuesday, and will finally peak on Thursday, as daytime high temperatures climb into the lower to middle 30s for just about everyone throughout southern Ontario and southern Quebec. Widespread heat warnings are in effect.

RELATED: How the humidex is calibrated to your body

Humidex values could climb as high as the mid-40s throughout the Greater Toronto and Hamilton Area (GTHA), in and around Ottawa, and across Montreal. Record-breaking humidex values are possible across the GTHA, with 45.6 being the all-time monthly record that was set on June 30, 2018 in Toronto.

Toronto 7 day forecast
Toronto 7 day forecast

Humidex records will be challenged all across Ontario, and will be similar in magnitude to the June-July 2018 heat wave event. As we continue to move in the direction of a warming world, extreme heat events like these are expected to increase in frequency.

On Tuesday, North Bay, Ont., experienced its ninth-hottest June day on record, while Wiarton, Ont., saw its fourth-hottest June day on record

On Wednesday, Ottawa tied its current record for its most humid June day with a humidex value of 44.

Oppressive temperatures will continue on Thursday, with a slight relief coming for Friday. It’ll continue to remain pretty warm and humid through the weekend.

humidex forecast Thurs
humidex forecast Thurs

Air quality in the region will likely suffer due to this stagnant, humid air mass.

Extreme heat has a compounding effect on your body. This level of heat could cause heat-related illnesses in even healthy individuals.

DON'T MISS: Too hot to sleep? These hacks can help whether you have AC or not

Any storms or clouds will help to cap daytime temperatures, even if only for a little while.

Thursday southern Ontario and Quebec storm risk map_June 19
Thursday southern Ontario and Quebec storm risk map_June 19

Thursday could bring a few scattered thunderstorms to parts of southern and eastern Ontario, extending into southern Quebec. It may offer some brief relief from the heat, though at the risk for periods of heavy rain, small hail and strong winds if any severe storms develop.

The chance for thunderstorms spills well into this first weekend of summer, as well.

SEE ALSO: There’s a dog in a hot vehicle! What should I do?

WATCH: Most surprising ways to beat the heat this summer

Click here to view the video

Increased potential for heat-related illnesses

Extreme heat is a leading weather-related cause of death around the world, claiming more lives every year than tornadoes and hurricanes combined. Hot temperatures are truly a silent killer.

Explainer: Heat Stroke, heat exhaustion symptoms, health
Explainer: Heat Stroke, heat exhaustion symptoms, health

Folks who are highly susceptible to the heat include those in homes without air conditioning, elderly people, unhoused people, outdoor workers, those living with chronic health conditions, and folks taking certain medications.

Check on vulnerable friends, family, and neighbours over the coming week. Stay alert for the signs of heat-related illnesses.

MUST SEE: Heat emergencies: How to spot them and what to do

Explainer: Confidence in attribution of different extreme heat events
Explainer: Confidence in attribution of different extreme heat events

Heat exhaustion occurs when a person’s body temperature climbs too high and they struggle to cool off. Symptoms of heat exhaustion include dizziness, excessive sweating, and weakness. Developing heat exhaustion is a serious sign that your body is in distress and you need to find a way to cool off immediately.

Heat stroke is a life-threatening medical emergency that occurs when a person’s body temperature is so high that their vital systems begin to shut down.

During heat stroke, sweat production stops and body temperatures soar very quickly. A victim suffering from heat stroke may exhibit confusion and loss of consciousness. Heat stroke can be fatal if not treated immediately.

Why heat waves aren’t ‘just summer weather’

The risk for heat-related illnesses will sharply increase during this upcoming heat wave as a result of the expected duration of hot temperatures and high humidity.

Humid air retains heat better than dry air, so nighttime temperatures won’t cool off enough to provide meaningful relief for folks without reliable access to air conditioning.

extreme heat safety tips
extreme heat safety tips

SEE ALSO: Five horrible things extreme heat does to the human body

Hot days running into stuffy nights will compound the effects of high heat on the human body, resulting in an increased potential for heat exhaustion and heat stroke.

Simply circulating air with fans won’t be enough to provide necessary relief from this level and duration of high heat. Air conditioning is a vital survival tool during a days-long heat wave.

Take advantage of community cooling centres if they’re available. Stay well-hydrated throughout the week, and avoid strenuous work outdoors during the heat of the day.

Stay with The Weather Network for all the latest on this impending heat wave.

Thumbnail image courtesy: Getty Images

WATCH: How living in a heat dome can impact your body

Click here to view the video