Extreme heat warning, severe thunderstorm watch in effect for Ottawa on Canada Day

A hot, humid day at Kiweki Point in Ottawa. June 11, 2026. (CTV News Ottawa)

Environment Canada is warning of extreme heat as well as severe thunderstorms in the Ottawa area on Canada Day.

On Wednesday, Environment Canada issued an orange warning-heat early in the morning, warning of 35 C temperatures throughout the day. In the afternoon, the organization issued a yellow watch, followed by a yellow warning, for severe thunderstorms.

Severe thunderstorms

Shortly after 2:30 p.m., Environment Canada issued a warning, advising resident that meteorologists are tracking a severe thunderstorm “capable of producing strong wind gusts, up to quarter size hail and very heavy rain.”

“Heavy rain may cause flash flooding and significant reductions to visibility,” Environment Canada said.

“There is a risk of injury. Take immediate cover if a thunderstorm approaches. If outside, protect yourself from flying debris and hail. If you hear roaring wind, see a funnel cloud, flying debris, or any threatening weather approaching, take shelter immediately.”

A thunderstorm watch was issued shortly before 1:30 p.m., with the forecaster saying conditions were favourable for severe thunderstorms. Environment Canada says thunderstorms could arrive in the afternoon or evening and may develop quickly.

“When thunder roars, go indoors! Lightning kills and injures Canadians every year,” Environment Canada wrote.

Both the severe thunderstorm watch and warning are currently in effect.

Extreme heat warning

According to Environment Canada, the temperature will reach a high of 35 C on Wednesday, and the humidex may reach 46. The overnight low is only expected to be 23 C.

“Heat warnings are issued when very high temperature or humidity conditions are expected to pose an elevated risk of heat illnesses, such as heat stroke or heat exhaustion,” Environment Canada said.

The orange level on Environment Canada’s colour-coded scale refers to weather that is likely to cause significant damage, disruption or health impacts. Environment Canada is advising residents to take steps to protect themselves from the heat.

“Determine if you or others around you are at greater risk of heat illness. Check on older adults, those living alone and other at-risk people in-person or on the phone multiple times a day,” Environment Canada wrote.

“Watch for the early signs of heat exhaustion in yourself and others. Signs may include headache, nausea, dizziness, thirst, dark urine and intense fatigue. Stop your activity and drink water.”

If someone is displaying signs of heat stroke, including red and hot skin, dizziness, nausea, confusion and loss of consciousness, 911 should be contacted immediately.

“While you wait for medical attention, try to cool the person by moving them to a cool place, removing extra clothing, applying cold water or ice packs around the body,” Environment Canada wrote.

• How to deal with heat exhaustion and heat stroke

Environment Canada recommends taking the following steps to deal with the heat:

• Limit exposure to the sun and heat
• Wear lightweight and light-coloured clothes
• Close blinds and shades, and open windows if it is cooler outside than inside
• Turn on air conditioning and use fans
• Move to cooler areas of your living space
• If there are no cool areas in your living space, move to a cool public place like a pool, cooling centre, community centre or library
• Drink water before you feel thirsty to replace fluids

The organization says air quality may be poor due to the heat and humidity, and the UV index is expected to reach 9 or higher.

Both the orange warning-heat and yellow watch-sever thunderstorm cover much of eastern Ontario and a full look at the warning zones can be found on Environment Canada’s website.

Forecast

The heat warning is expected to continue through the weekend, with Wednesday and Thursday being the hottest days.

Thursday’s forecast predicts another day of 34 C, with a 40 per cent chance of showers.

On Friday, expect 33 C and a chance of showers.

On Saturday, expect 31 C and a chance of showers.

On Sunday, temperatures are expected to dip below 30 C, reaching a high of only 29 C.

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