Goddard Earth Observing System (GOES) model of North American air temperature anomalies at 2 metres on 27th June 2021. Red areas are 15 degrees Celsius hotter than the 2014-2020 average for the same day. During late June a heatwave in the Pacific Northwest led to all-time record temperatures in a number of US and Canadian cities. It was caused by a strong flow of air moving from east to west, pushing cool ocean air away from the land. The flow was due to exceptionally high pressure inland and low pressure near the coast.