The effects of extreme warming have been felt across the globe in recent years, especially with intensely hot summers in eastern Asia, western Europe, and North America. On July 21, 2017, a weather station in Shanghai, China, recorded a high temperature of 40.9 degrees C (105.6 degrees F), the highest temperature recorded at that location since 1873. To understand what caused the extremely hot summer for South and Central China, a scientific collaboration of climatologists examined how abnormal sea surface temperatures and atmospheric circulation could co-influence regional temperatures over land.