The weather agency said daytime temperatures for most of the affected areas will reach 31 C to 33 C, with humidex values of 42 to 43.
“Overnight low temperatures on Wednesday night of 21 to 23 C will provide minimal relief from the heat,” Environment Canada said.
In the Windsor area, the weather agency is forecasting a high of 34 C with a humidex of 45. Overnight lows there are expected to be 23 C.
“Hot and humid air can also bring deteriorating air quality and can result in the Air Quality Health Index approaching the high risk category,” the statement said.
A special weather statement is different to a heat warning.
Environment Canada noted that despite the hot conditions, a heat warning is not required as temperatures will not meat the criteria with a cold front passing through Thursday.
“Heat warnings require hot and humid conditions (temperatures of 31 C or humidex values of 40) to last for two days, including the overnight low in between to be 20 C or higher,” the statement said.
“In this case, a special weather statement has been selected to highlight that these conditions may pose a health risk.”