We studied the effects of extreme heat on urban trees in Western Sydney during Australia’s record-breaking summer of 2019–20. So we hold grave concerns for the survival of both native Australian and exotic species in our urban forest. These stands of trees and shrubs – along streets and in parks, gardens, and yards – play vital roles in our cities. Trees improve people’s mental health and wellbeing, lower energy use, and reduce temperatures through shading and evaporative cooling.