Environment Canada has issued a heat warning for southern Ontario which calls for the affected area to see extreme temperatures from Wednesday through Friday.
The warning extends from Windsor and Niagara Falls right over to Oshawa and Owen Sound and includes London, Kitchener, Guelph, Hamilton and the entire GTA.
The agency says that on Wednesday, temperatures are expected to reach 30 C and while they will cool slightly on Thursday, the humidex is expected to reach the high-30s.
Friday is forecast to be a scorcher as Environment Canada says that humidex values will reach 40 in many areas while there will be little relief from the heat as the lows will be in the 20s.
The area is not expected to find relief until Saturday when cooler temperatures arrive.
With higher temperatures in the forecast, the agency says they will pair with deteriorating air quality which will push the the Air Quality Health Index into the high-risk category.
“Watch for the effects of heat illness: swelling, rash, cramps, fainting, heat exhaustion, heat stroke and the worsening of some health conditions,” the warning notes.
It also advises those who are feeling the heat to drink plenty of water and try to camp out in a cool place if possible.
The warning says people should check on older family and friends to make sure they are cool and drinking water while also noting that people and pets should not be left in vehicles.
Those who are working outside over the next few days should take regular breaks in cool places as well.
Environment Canada says that areas around large bodies of water will be cooler than those inland.