Plain Language Summary

Western North America experienced the most severe extreme heat event (EHE) ever recorded in the region during the summer of 2021. There were approximately 740 more deaths than usual in British Columbia (BC), Canada during the EHE, which made it one of the deadliest weather events in Canadian history. This study compares people who died during the EHE with people who died at the same time of year in other years to identify differences between the two groups with respect to 26 chronic diseases. We found that people with schizophrenia had the most significantly elevated risk of death during the EHE. People with chronic kidney disease and ischemic heart disease were also at increased risk. This information will be used to help develop programs that support people at higher risk during future EHEs.