Overview of Latest Heat Warning: Weather alerts
Multiple active bulletins issued for this subscription.
Latest bulletin issued on Sunday June 22, 2025 05:43 EDT by Environment Canada.
- Dunnville - Caledonia - Haldimand, Ont. (041200) Sunday June 22, 2025 05:43 EDT
- City of Toronto, Ont. (043100) Sunday June 22, 2025 05:43 EDT
- Newmarket - Georgina - Northern York Region, Ont. (043220) Sunday June 22, 2025 05:43 EDT
- Vaughan - Richmond Hill - Markham, Ont. (043240) Sunday June 22, 2025 05:43 EDT
- Barrie - Orillia - Midland, Ont. (044100) Sunday June 22, 2025 05:43 EDT
- Bracebridge - Gravenhurst, Ont. (044440) Sunday June 22, 2025 05:43 EDT
- City of Hamilton, Ont. (046100) Sunday June 22, 2025 05:43 EDT
- Owen Sound - Blue Mountains - Northern Grey County, Ont. (046220) Sunday June 22, 2025 05:43 EDT
- Listowel - Milverton - Northern Perth County, Ont. (046320) Sunday June 22, 2025 05:43 EDT
- Stratford - Mitchell - Southern Perth County, Ont. (046340) Sunday June 22, 2025 05:43 EDT
- Waterloo - Wellington, Ont. (046400) Sunday June 22, 2025 05:43 EDT
- Innisfil - New Tecumseth - Angus, Ont. (046510) Sunday June 22, 2025 05:43 EDT
- Halton Hills - Milton, Ont. (046630) Sunday June 22, 2025 05:43 EDT
- Burlington - Oakville, Ont. (046640) Sunday June 22, 2025 05:43 EDT
- Niagara, Ont. (046700) Sunday June 22, 2025 05:43 EDT
- Searchmont - Montreal River Harbour - Batchawana Bay, Ont. (048820) Sunday June 22, 2025 05:32 EDT
- Sault Ste. Marie - St. Joseph Island, Ont. (048830) Sunday June 22, 2025 05:32 EDT
- Greater Sudbury and vicinity, Ont. (049100) Sunday June 22, 2025 05:32 EDT
- Elliot Lake - Ranger Lake, Ont. (049200) Sunday June 22, 2025 05:32 EDT
- Temiskaming Shores - Temagami, Ont. (049720) Sunday June 22, 2025 05:32 EDT
- North Bay - West Nipissing, Ont. (049800) Sunday June 22, 2025 05:32 EDT
- Manitoulin - Blind River - Killarney, Ont. (049900) Sunday June 22, 2025 05:32 EDT
Public Alert Areas Map
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Active Heat Warning
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Alert Details
Issued on Sunday June 22, 2025 05:43 EDT
- Dunnville - Caledonia - Haldimand, Ont. (041200)
- City of Toronto, Ont. (043100)
- Newmarket - Georgina - Northern York Region, Ont. (043220)
- Vaughan - Richmond Hill - Markham, Ont. (043240)
- Barrie - Orillia - Midland, Ont. (044100)
- Bracebridge - Gravenhurst, Ont. (044440)
- City of Hamilton, Ont. (046100)
- Owen Sound - Blue Mountains - Northern Grey County, Ont. (046220)
- Listowel - Milverton - Northern Perth County, Ont. (046320)
- Stratford - Mitchell - Southern Perth County, Ont. (046340)
- Waterloo - Wellington, Ont. (046400)
- Innisfil - New Tecumseth - Angus, Ont. (046510)
- Halton Hills - Milton, Ont. (046630)
- Burlington - Oakville, Ont. (046640)
- Niagara, Ont. (046700)
Dangerous heat and humidity beginning this afternoon.
The first significant heat event of the season with dangerously hot and humid conditions will begin this afternoon and is expected to continue into the week.
What:
Daytime highs of 30 to 36 degrees Celsius.
Humidex values of 40 to 45.
Overnight lows of 21 to 25 degrees Celsius, providing little relief from the heat.
When:
This afternoon until Tuesday night.
Additional information:
The extreme heat and humidity may continue into Wednesday. A cold front is expected to push through the region late Tuesday, but there is some uncertainty with how far south this front will get. Should it remain farther north, the heat event may continue Wednesday, primarily for southwestern Ontario and the GTA.
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.
For more information: https://www.canada.ca/en/health-canada/services/climate-change-health/extreme-heat/how-protect-yourself.html https://www.canada.ca/en/health-canada/services/climate-change-health/extreme-heat/who-is-at-risk.html
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.
Issued on Sunday June 22, 2025 05:32 EDT
- Searchmont - Montreal River Harbour - Batchawana Bay, Ont. (048820)
- Sault Ste. Marie - St. Joseph Island, Ont. (048830)
- Greater Sudbury and vicinity, Ont. (049100)
- Elliot Lake - Ranger Lake, Ont. (049200)
- Temiskaming Shores - Temagami, Ont. (049720)
- North Bay - West Nipissing, Ont. (049800)
- Manitoulin - Blind River - Killarney, Ont. (049900)
The first significant heat event of the season with dangerously hot and humid conditions will begin this afternoon.
What:
Daytime highs of 29 to 33 degrees Celsius.
Humidex values near 40.
Overnight lows of 18 to 21 degrees Celsius, providing little relief from the heat.
When:
This afternoon to Monday night.
Additional information:
A cold front is expected to push through the region Monday night, but there is some uncertainty with how far south this front will get. Should it remain farther north, the heat event may continue for Tuesday primarily for Sudbury, West Nipissing, North Bay and Espanola - Killarney regions.
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.
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.
For more information: https://www.canada.ca/en/health-canada/services/climate-change-health/extreme-heat/how-protect-yourself.html https://www.canada.ca/en/health-canada/services/climate-change-health/extreme-heat/who-is-at-risk.html
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.
Latest information is always available here:
https://weather.gc.ca/index_e.html?layers=alert
Latest Alert Version: Weather alerts
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