TORONTO, August 8, 2025 – Toronto, and pretty much everywhere else in southern Ontario are about to be hit with yet another heat wave—in fact, we have lost count but we think it is our sixth heat warning this summer—starting on Saturday and continuing at least until Wednesday, when daytime highs are expected to dip a teensy bit from 30 – 33ºC, with humidex values of 35 to 40, to around 28ºC.
Heat warning in effect until Wednesday for the following regions (but basically, everywhere):
Simcoe – Delhi – Norfolk; Dunnville – Caledonia – Haldimand; Watford – Pinery Park – Eastern Lambton County; Sarnia – Petrolia – Western Lambton County; Chatham-Kent – Rondeau Park; Windsor – Leamington – Essex County; London – Parkhill – Eastern Middlesex County; Strathroy – Komoka – Western Middlesex County; St. Thomas – Aylmer – Eastern Elgin County; Rodney – Shedden – Western Elgin County; Woodstock – Tillsonburg – Oxford County; Brantford – County of Brant; City of Toronto; Uxbridge – Beaverton – Northern Durham Region; Newmarket – Georgina – Northern York Region; Pickering – Oshawa – Southern Durham Region; Vaughan – Richmond Hill – Markham; Belleville – Quinte West – Eastern Northumberland County; Cobourg – Colborne – Western Northumberland County; Tamworth – Sydenham – South Frontenac; Stirling – Tweed – Madoc; Kingston – Odessa – Frontenac Islands; Napanee – Consecon; Picton – Sandbanks Park; Merrickville-Wolford – Kemptville; Westport – Charleston Lake; Brockville – Prescott; Gananoque – Mallorytown; Maxville – Alexandria; Cornwall – Lancaster; Winchester – Newington; Morrisburg – Long Sault; Bancroft – Hastings Highlands – Denbigh; Kaladar – Bannockburn – Bon Echo Park; Apsley – Woodview – Northern Peterborough County; Lindsay – Southern Kawartha Lakes; Peterborough City – Lakefield – Southern Peterborough County; Prescott and Russell; Petawawa – Pembroke – Cobden; Barry’s Bay – Killaloe; Renfrew – Arnprior – Calabogie; Smiths Falls – Perth – Eastern Lanark County; Plevna – Sharbot Lake – Western Lanark County; Ottawa North – Kanata – Orléans; Ottawa South – Richmond – Metcalfe; City of Hamilton; Guelph – Erin – Southern Wellington County; Kitchener – Cambridge – Region of Waterloo; Caledon; Mississauga – Brampton; Halton Hills – Milton; Burlington – Oakville; St. Catharines – Grimsby – Northern Niagara Region; Niagara Falls – Welland – Southern Niagara Region
What:
Multi-day heat event beginning Saturday. What: Daytime highs of 30 to 33 degrees Celsius, with humidex values of 35 to 40. Overnight lows of 19 to 23 degrees Celsius.
When:
Beginning on Saturday and continuing until Wednesday evening.
Additional information:
Slightly cooler temperatures are expected by the middle of next week, bringing an end to this heat event.
What to do:
Take action to protect yourself and others – extreme heat can affect everyone’s health. 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.
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.
Heat stroke is a medical emergency! Call 9-1-1 or your emergency health provider if you, or someone around you, is showing signs of heat stroke which can include red and hot skin, dizziness, nausea, confusion and change in consciousness.
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. Drink water often and 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. Follow the advice of your region’s public health authority.
Plan and schedule outdoor activities during the coolest parts of the day. Limit direct exposure to the sun and heat. Wear lightweight, light-coloured, loose-fitting clothing and a wide-brimmed hat.
Never leave people, especially children, or pets inside a parked vehicle. Check the vehicle before locking to make sure no one is left behind.
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.
For more information: How to protect yourself from the health effects of extreme heat Health risks and who is at risk of extreme heat events
Please continue to monitor alerts and forecasts issued by Environment Canada. To report severe weather, send an email to ONstorm@ec.gc.ca or post reports on X using #ONStorm.
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