Why this summer may be especially hot in the United States

The probable switch from El Niño to La Niña increases the risk of a hot summer and possibly the hottest on record

https://www.washingtonpost.com/weather/2024/04/22/summer-forecast-united-states-hot/

https://archive.ph/Ew9pX



A new outlook for summer from the National Weather Service is a toasty one: Hotter-than-normal conditions are favored almost everywhere, except for a small portion of the northern Plains. The highest odds for a hot summer stretch from Texas into the Pacific Northwest, as well as much of the Northeast. This forecast sets the stage for bouts of record-challenging high temperatures throughout the nation and the possibility of the hottest summer ever observed. In the central states and Rocky Mountains, the combination of heat and an expectation for drier-than-normal weather will increase drought potential. It will also raise the fire threat in some areas.

Weather Service officials and the Centers for Disease Control and Prevention on Monday stressed the importance of preparation for the heat as they unveiled a heat forecast guide that will be used across the United States for the first time this year. Already used for years in the West, the HeatRisk forecast will use a color-coded scale to describe the health risks expected from heat waves over the coming seven days. “It’s giving us knowledge we can use to take steps to protect our health if we need to,” said Aaron Bernstein, director of the CDC’s National Center for Environmental Health. “We’ll be able to know how hot is too hot for health.”

The hot summer forecast is linked to the probable switch from the El Niño to La Niña climate pattern by the summer’s second half. While La Niña has a small cooling effect on the planet overall, it has boosted summer heat in the United States, especially in recent years when human-caused climate change has also fueled higher temperatures. The three La Niña summers from 2020 to 2022 were all historically hot. The nation’s summer average temperature of 74 degrees in 2021 was tied for the hottest on record; 2022 and 2020 marked the third- and sixth-hottest summers, respectively.



“A common feature in summer during a developing La Niña is a semi-permanent upper-level ridge over the middle of North America,” wrote DTN, a forecasting company based in Minneapolis. “Ridges are notorious for hot and dry conditions.” These ridges, referred to as heat domes, are common in summer but tend to be most persistent during La Niña. A hot summer often goes hand in hand with drought, as high temperatures increase evaporation, which strips moisture from the land surface. The driest weather compared to normal is expected to stretch from western Texas into the northern Rockies. The Weather Service predicts drought will persist or develop in much of this region.

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