‘Dangerously hot’: Weather alerts in effect for weekend highs

Climate scientist Paul Beckwith discusses summer heat wave risks, what's causing them, and tornado threats in Saskatchewan.

Environment Canada has more than 200 active weather and air quality alerts this weekend, including extreme heat warnings across much of Ontario and Quebec.

Here’s what to know:

Extreme heat alerts

“The first significant heat event of the season with dangerously hot and humid conditions will begin Sunday afternoon and is expected to continue into the week,” reads one of several heat-related alerts.

As of Sunday morning, a wide area is under a severe heat warning including all of southern Ontario and Quebec, from Sault Ste. Marie, Ont., in the west, to Windsor, Ont., in the south, to Val-d’-Or, Que., in the north, to Sherbrooke, Que., in the east.

Within that zone, daytime temperatures are expected to reach as high as 31 to 36 degrees Celsius in some areas between now and mid-week, with a humidex of near or above 40.

Temperatures will fall to high teens or low-to-mid 20s overnight, though Environment Canada notes that will be “providing little relief from the heat.”

A humidex of near 40 has sparked a special weather statement for the Quebec City area, as well as a region from La Tuque, Que., north toward Lac Saint-Jean.

A heat warning is also in effect for the area along Ontario’s southern border with Minnesota from Saturday into late Sunday, when temperatures are expected to reach between 28 and 30 degrees with overnight lows near 18 and humidex values close to 40.

In northwestern Yukon, a special weather statement notes a “prolonged period of elevated temperatures” is expected this weekend, with daytime highs in the mid to high 20s.

Residents in affected areas are advised to stay hydrated, seek out air conditioning, fans or shade, use ice packs and local cooling centres, and monitor for symptoms of heat exhaustion, including headaches and dizziness, nausea, thirst, dark urine and “intense fatigue,” Environment Canada says.

Additional symptoms such as a change in consciousness, red and hot skin and confusion may be signs of heat stroke, which the agency notes is a medical emergency.

In the event of a heat stroke, you should call 9-1-1 and cool the person down while awaiting medical attention, Environment Canada says, such as by removing extra clothing, moving them to a cooler location and applying ice packs and cold water to their body.

• READ MORE: Signs of trouble to watch out for in extreme heat

Aside from the heat, a special weather statement is in effect for the southeast corner of Manitoba, where showers and thunderstorms are expected to begin around midday Sunday, including potential “torrential downpours and localized overland flooding.”

A patchwork of rain measuring between zero and 75 millimetres is forecast, though some areas may see as much as 100 if “impacted by multiple thunderstorms in succession.”

Storm activity is expected to subside by Sunday evening.

Air quality alerts

In addition to this weekend’s weather alerts, air quality alerts linked to wildfire smoke are active in regions across western Canada, including in northwestern Ontario, eastern Manitoba, central Saskatchewan and in northern Alberta and British Columbia.

“As smoke levels increase, health risks increase,” Environment Canada warns, advising those in affected areas to limit time spent outside and to consider rescheduling sporting events and other activities.

Windows and doors should be kept closed as much as possible, and tools including ventilation with quality air filters, portable air cleaners and well-fitting respirator-type masks are recommended, though risks to health may persist.

Those especially vulnerable to poor air quality include people aged 65 or older, pregnant people, infants and young children, people with existing illnesses or health conditions and those who work outdoors.

Residents are advised to check in on neighbours and others in their care, particularly those who are vulnerable.

You can view active alerts and other information at Environment Canada’s weather information system here.