Thunderstorms possible as the heat wave continues in southwestern Ontario

Storm clouds as seen from Upper Ratho in Blandford-Blenheim Township on July 3, 2026. (Courtesy: Linda Reid)

The heat wave continues in southern Ontario.

Friday’s forecast showed a high of 31 degrees Celsius, but Environment Canada said it could feel closer to 38.

That is somewhat of an improvement from Wednesday and Thursday, when the humidex climbed above 45.

Environment Canada also issued another thunderstorm watch on Friday afternoon. The agency said conditions were favourable for strong wind gusts of up to 100 km/h, as well as ping pong ball-sized hail and heavy rain, possibly exceeding 30 mm.

When will the heat wave end?

The hot weather will be sticking around into next week.

Environment Canada’s forecast showed a high of 29 degrees Celsius on Saturday, but feeling closer to 35. Waterloo Region could also see a mix of sun and cloud during the day, with a 40 per cent chance of showers, or even a thunderstorm, in the afternoon.

The agency also predicted a high of 24 degrees Celsius on Sunday, with cloudy skies and a 30 per cent chance of showers.

The forecast for the rest of the week could change but, as of Friday afternoon, it ranged from a high of 25 to 28 degrees Celsius without factoring in the humidex.

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, mobility issues, people 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, by comparison, is considered a medical emergency.

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

Never leave pets inside a hot vehicle.

Dogs can also experience heatstroke, and it could lead to organ failure or even 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.

Anyone concerned about the well-being of an animal is advised to call 911.