From June 25 to July 2, 2021, the Pacific Northwest experienced a record-breaking heat wave that sent the normally temperate region into Death Valley-like extremes that took a heavy toll on trees as well as people. Seattle and Portland, Ore., recorded their hottest-ever temperatures, reaching 108 degrees Fahrenheit (42.2 Celsius) and 116 Fahrenheit (46.6 Celsius), respectively. …But, as recent research suggests, tree foliage didn’t simply dry out in the heat dome. Instead, it underwent “widespread scorching.” “A lot this reddening and browning of leaves was just that the leaves cooked. It really wasn’t a drought story,” said Chris Still, professor at Oregon State University’s College of Forestry and a leading researcher on the effects of heat on trees. …“Plants can control their temperature to some degree, but if the heat is extreme enough, some plants won’t be able to get through it even if they have a ton of water,” he said.