Environment Canada issues week-long heat warning across southwestern Ontario

A yellow-level warning is in place for much of southwestern Ontario as Environment Canada states a "long-duration heat event" begins Monday.

Until Friday, and possibly into the weekend, maximum temperatures could reach 36 C, only dropping to 21 to 25 degrees. Humidex values are expected to remain between 37 and 45 C.

It will feel "notably hotter and a little bit more humid" on Monday, according to Daniel Sheldon, a meteorologist with Environment Canada, with a high of 30 C and a humidex value of 38 C.

"The heat and humidity will continue to build Tuesday onward through the end of the week," he said.

"The thing with this event is that it will last the better part of the week, so at least five days," he said. "Our overnight lows are going to remain in the low to mid 20s, so there's not really a break."

The only possible reprieve, he added, would be if thunderstorms occur, but he said the "chances are kind of low," he said.

Watch for signs of heat exhaustion in yourself and others, Environment Canada warned, with signs including headache, nausea, dizziness, thirst, dark urine and intense fatigue. If any of these signs are present, it added, stop any activities and drink water.

"Stay hydrated and take lots of breaks, if you happen to be outside or having to do any activities outside," Sheldon said.

"Check in with the folks that are more susceptible to the heat, as well."

Heat stroke is a medical emergency, and signs can include red or hot skin, dizziness, nausea, confusion and change in consciousness.

Call 911 or an emergency health provider if these symptoms occur in yourself or others, Environment Canada advised, adding that while you wait for medical attention, try to cool the person by moving them to a cool place, removing extra clothing, and applying cold water or ice packs around the body.

Other tips provided by the weather agency include:

• Drink water often, before you feel thirsty, to replace fluids.
• Close blinds or shades, and open windows if outside is cooler than inside.
• Turn on air conditioning, use a fan, or move to a cooler area of your living space. If your living space is hot, move to a cool public space such as a cooling centre, community centre, library or shaded park.
• Plan or schedule outdoor activities during the coolest parts of the day.
• Limit direct exposure to the sun and heat, wearing lightweight, light-coloured, loose fitting clothing and a wide-brimmed hat.
• Never leave people, especially children or pets, inside a parked vehicle.
• Follow the advice of your regions public health authority.

Sheldon also recommended escaping to the shores of Lake Erie, if possible. Stretches of that shoreline closer to the London area are expected to have more manageable temperatures with no heat warning in effect.