Heat warning continues in southern Ontario

Sunset seen in Cambridge, Ont. on April 29, 2025. (Courtesy: Don Thomas)

A heat warning remains in place for Waterloo Region and communities across southern Ontario.

Daytime temperatures on Tuesday could reach 31 to 34 degrees Celsius. With the humidex, it could feel closer to 37 to 42 degrees Celsius. Overnight, the mercury is only expected to drop to 19 or 21 degrees Celsius.

Environment Canada said southern Ontario will get a break from the heat on Thursday night.

Air quality was also a concern on Monday as wildfire smoke drifted south from northern Ontario and western provinces.

While most of those warnings have since ended, as of Tuesday afternoon, Environment Canada’s air quality index for Waterloo Region, Guelph and surrounding areas remained at level 5, which is considered a moderate risk.

Air pollution can be harmful to the health of seniors, pregnant people, infants, children, those who work outdoors or anyone with a chronic illness.

It could also cause a respiratory emergency when coupled with the high heat, according to a University of Guelph professor who spoke with CTV News on Monday.

Signs of heat illness

Heat illness is a serious concern when the mercury rises, especially in older adults, infants, young children, pregnant people, those with physical or mental illnesses, people with mobility issues, those who work outside and the homeless community.

Symptoms of heat exhaustion include:

• Headache
• Nausea or vomiting
• Dizziness or fainting
• Extreme thirst
• Dark urine and decreased urination
• Intense fatigue
• Confusion or lack of coordination
• Skin rash
• Muscle cramps
• Heavy sweating
• Rapid breathing and heartbeat

Heat stroke, meanwhile, is considered a medical emergency.

Those symptoms include:

• High body temperature
• Very hot, red skin
• Confusion or change in consciousness
• Dizziness or fainting
• No sweating

If someone is experiencing heat stroke, experts advise moving them to a cool place, giving them water and placing ice packs on their body. Call 911 immediately.

Beating the heat

The key to avoiding heat illness is to plan ahead.

Here are a few things to keep in mind:

• Know the weather forecast before going outside
• Modify your plans according to the weather
• Drink plenty of cool liquids, especially water, even before you feel thirsty
• Avoid drinks that are high in sugar, caffeine or alcohol
• Wear loose-fitting, light-coloured clothing made of breathable fabric
• Seek shade
• Avoid sun exposure if you can
• Take breaks as needed
• Avoid using your oven
• Take a cool shower or bath
• Take a break by spending a few hours in a cool place
• Close blinds and shades,
• Turn on air conditioning or use a fan

Cooling centres

The best way to get relief from the heat and humidity is to seek out a designated cooling centre.

The Region of Waterloo has locations listed on their website. They include libraries, community centres, museums and regional offices.

The map also includes a list of public swimming pools and splash pads.

Protecting your pets

Leaving pets inside a hot vehicle, even for a few minutes, could be dangerous.

Dogs can experience heatstroke, which could lead to organ failure and, ultimately, death.

Signs of an overheated pet include:

• Excessive panting
• Drooling
• Vomiting
• Collapsing
• Lethargy
• Tongue can appear red or hang out of their mouth

If your pet is suffering from the heat, it’s a good idea to gradually cool them down.

Experts suggest using a cool blanket or towel that is wet. Avoid using ice.

Owners should keep pets at home when the temperature climbs but if they need to go outside, keep them off the pavement as much as possible, only go for a short walk, or take them out in the morning or evening when it’s cooler.