The heat wave that scorched the Pacific Northwestern United States in late June rewrote the record books in ways that were both shocking and difficult to comprehend. Scientists are unsure how best to explain the temperatures, so extreme compared with what meteorologists expect to see in that typically cool, wet region of the world.

In Seattle, Washington, temperatures hit 108 degrees Fahrenheit, 9 degrees hotter than it’s ever been in steamy Tampa, Florida. Portland, Oregon’s 116°F eclipsed Dallas, Texas’s heat record by 3 degrees. Hundreds of miles north of Portland, the British Columbia village of Lytton set a new temperature record for Canada—a Death Valley-like 121 degrees. The next day, the town was engulfed and