Against the background of global warming, extreme heat has occurred more frequently and caused adverse socioeconomic effects. In the midsummer of 2018, a severe extreme heat episode struck Northeast Asia, causing numerous fatalities. For instance, the extreme heat that struck Japan in July 2018 resulted in about 24,000 hospitalized patients and more than 90 deaths. To understand what caused the extreme heat over Northeast Asia, a scientific collaboration of climatologists examined the forces of the tropical circulation and sea surface temperature. Their results have recently been published in Atmospheric and Oceanic Science Letters.