Heat warnings are in effect for most of southern Ontario on Tuesday.
The three-day heat event continues through Wednesday in London-Middlesex and surrounding areas with maximum temperatures to reach the mid 30s, according to Environment Canada.
Minimum temperatures tonight and Wednesday night are forecast to be in the low 20s and will provide little relief from the heat. Cooler air is expected to arrive by Thursday.
The weather authority also warns that hot and humid air can also bring deteriorating air quality and can result in the air quality health Index approaching the high risk category.
Check on older family, friends and neighbours. Make sure they are cool and drinking water.
Tuesday: Sunny. High 33. Humidex 39. UV index 10 or very high.
Tuesday Night: Clear. Becoming partly cloudy after midnight. Low 22.
Wednesday: Sunny early in the morning then a mix of sun and cloud with 30 per cent chance of showers late in the morning and early afternoon. Risk of a thunderstorm late in the morning and early afternoon. High 29. Humidex 35. UV index 11 or extreme.
Thursday: Sunny. High 28.
Friday: Sunny. High 30.
Saturday: A mix of sun and cloud. High 30.
Sunday: A mix of sun and cloud. High 26.