The warning from the national weather service covers large areas of southern Ontario, Nova Scotia, Alberta and B.C. Environment Canada says highs are expected to reach or exceed 30 C and reach the low forties when combined with humidity. Cooler temperatures are forecast to return Monday night or Tuesday for most areas. However, heat is expected to return to parts of Alberta on Wednesday. Heat warnings are issued when very high temperature or humidity conditions are expected to pose an increased risk of heat illness, such as heat stroke or heat exhaustion. This report by The Canadian Press was first published on August 8, 2022