Environment Canada has issued another orange heat warning for the London, Ont., area and surrounding counties in southwestern Ontario. The long duration heat event continues. For some areas, this is the first heat event of the season. Maximum temperatures of 31 to 35 Celsius are in the forecast for Wednesday and potentially up to 37C for some areas. Minimum temperatures of 21 to 25C. The heat is expected to continuing through Friday, and possibly into the weekend. Additional Information: The hottest days are expected today through Thursday, with maximum temperatures of 35 to 37C expected. Hot and humid air can also bring deteriorating air quality and can result in the Air Quality Health Index approaching the high-risk category. Here’s a look at the extended forecast: Thursday: Sunny early in the morning then a mix of sun and cloud with 40 per cent chance of showers in the afternoon. Risk of a thunderstorm in the afternoon. High 33 Friday: A mix of sun and cloud with 40 per cent chance of showers. High 33. Saturday: A mix of sun and cloud with 40 per cent chance of showers. High 31. Sunday: A mix of sun and cloud with 30 per cent chance of showers. High 28. Monday: A mix of sun and cloud. High 28.