Summer is being replaced by the season of extreme heat
Summer is hot. This is among the most basic weather concepts that we learn as children and accept without question. Heat and even heat waves have always been a reliable hallmark of the season between the June solstice and the September equinox. And yet recent weather has far outstripped that norm. For most of last week, the daily high temperature in Phoenix reached or exceeded 115 degrees, breaking records even in that desert city. This weekend, a “heat dome” is expected to raise temperatures above 110 degrees in Washington, Oregon, and Idaho—places whose physical infrastructure is not well adapted to such heat.
Climate change is upending old rules and disrupting predictable weather patterns: Heat waves, wildfires, and tropical storms and hurricanes—the trifecta of extreme weather events—now arrive earlier than expected, occur with greater frequency and intensity, and stretch well past their historical timelines. But too few Americans think about heat waves, which claim more lives globally than any other weather-related hazard, as a problem for which systematic, long-term preparation is warranted. To protect human life as temperatures soar, we need to conceive of what we might call heat season as a phenomenon distinct from summer—a part of the year that people in much of the country have traditionally viewed with great fondness.
Historically, wildfire season in the United States has begun in May and ended in October; however, wildfires raged well into December last year. The 2020 season, which included 30 named storms, was the most active on record. The annual Atlantic hurricane season formally begins June 1 and ends November 30. The emergence of Tropical Storm Ana on May 22 made 2021 the seventh consecutive year that a storm strong enough to be named formed off-season. Because of this early storm activity, the National Weather Service has been considering moving the start of hurricane season to mid-May.
Heat waves, too, are arriving alarmingly early. Barely a week into summer, a heat dome affecting 40 million Americans lifted temperatures above 100 degrees not only in Phoenix but in places such as Denver, Salt Lake City, and Billings, Montana. Northern locations not typically plagued by extreme heat were hit even earlier. In early June, the city of Caribou in northern Maine experienced back-to-back highs of 92 degrees. [Continue reading…]