Heat waves are one of the deadliest natural hazards, and this one affected a population unaccustomed and unprepared for such extreme temperatures, the study said. Many homes in British Columbia, Oregon and Washington lack air conditioning. Wednesday's study was prepared by World Weather Attribution, an international collaboration that analyzes and communicates the possible influence of climate change on extreme weather events, such as storms, extreme rainfall, heat waves, cold spells and droughts. "We are entering uncharted territory," Seneviratne said. "The temperatures experienced in Canada last week would have broken records in Las Vegas or Spain. However, much higher temperature records will be reached if we don’t manage to stop greenhouse gas emissions and halt global warming."