Heat Wave Trends in Canadian Regions

Despite their widespread impacts, there has been limited work to quantify how heat waves have changed in Canada. With no standard definition of a heat wave, we consider two different types of heat waves: climatological heat waves defined by the exceedance of a climatological percentile threshold and heat-warning heat waves which are based on the absolute threshold criteria for issuing heat warnings in Canada. These two heat waves represent different types of events with different primary impacts. We find the type of heat wave strongly influences the number of heat waves each year and the regional patterns of where such events are more prevalent. After the evaluation of climatologies, considering station observations and spatially complete gridded datasets, trends in annual metrics of heat waves were calculated for Canadian regions. Climatological heat waves increased in frequency, duration, and cumulative intensity between 1961 and 2020 across the country and in most regions. Heat-warning heat waves have increased over Northern and Atlantic Canada.