This story is part of Record High, a Grist series examining extreme heat and its impact on how – and where – we live.
More than 113 million people in the United States are suffering from extreme heat while another massive “heat dome” extends west from Texas to California. Meteorologists expect the southwest heat wave to intensify over the weekend, delivering some of the highest temperatures of the year and pushing California’s Death Valley near its all time record temperature over 130 degrees Fahrenheit. The midday heat in cities like Phoenix, Arizona has become so intense that ordinary surfaces such as streets and metal railings are too dangerous to touch without the risk of getting burned.
But aside from those jaw-dropping highs, experts said the real danger from the southwest heatwave will be its duration. THE stagnant air mass event manager has already focused on Texas and Louisiana for weeks. It feeds on itself to generate more heat as it moves west, depleting soil moisture and discouraging cloud formation, ensuring it won’t go away before at least another week. Meanwhile, more than a third of the nation’s population will be under a heat warning issued by the National Weather Service.
Daytime highs in Phoenix have already topped 110 degrees F daily in July, and the city is expected to stay that hot for at least another week, smashing the previous record 18 consecutive days above this threshold. Additionally, large metropolitan areas like Phoenix will stay warm even in the middle of the night, as the heat seeps through the concrete and asphalt. Daily low temperatures in the nation’s fifth-largest city are not expected to fall below 90 degrees F for another week or more.
This long period of heat will have dire effects on human health, said Juan Declet-Barreto, a social scientist at the nonprofit Union of Concerned Scientists who studies climate vulnerability.
“The magnitude of these events in terms of predicted temperatures and duration is very, very, very concerning,” he told Grist. “It’s an absolute crisis.”
The populations most affected are outdoor workers and people who travel on foot or by public transport, since they cannot shelter from the heat in air-conditioned environments. If a heat wave only lasts for a day, some people can deal with it by staying indoors and blasting the air conditioning, but weeks of unrelenting heat make it difficult to avoid the exposure that can cause potentially fatal heat stroke.
And that’s not the only concern. A long period of triple-digit days can make it harder for the heart to pump blood and the lungs to move air, leading to flare-ups. heart disease and lung disease. Even for people who spend most of their time indoors with the air conditioning on, prolonged heat can lead to dehydration, irritability, confusion, and dizziness. For vulnerable populations like the elderly and obese, health effects may recur for years.
“The body loses the ability to self-regulate,” Declet-Barreto said of temperatures above 105 degrees F. “This is even more true for older populations, people with physical or mental disabilities who may not be able to communicate their level of discomfort, and people with fewer resources (who) will find it difficult to operate the air conditioner.
Large cities are even more vulnerable to long heat waves than rural areas due to what is known as the “urban heat island effect”. On a hot day, the sidewalks and buildings in a city like Phoenix soak up all the heat from the sun pouring down the city streets. At night, after sunset, they release all of this trapped heat into the surrounding air, which keeps local temperatures high even when there is no humidity. Also, people who can’t afford to run their AC all day can turn it off at night, leaving them exposed for hours.
“In southwestern cities like Phoenix that are naturally hot and also have a very brutal urban heat island effect, you’re not going to see any respite,” Declet-Barreto said. “The body doesn’t really get a chance to rest.”
A study published last year in the medical journal The Lancet found that an increase in nighttime temperatures is associated with a increased heat-related mortality. Most of the deaths are in the elderly, who can face serious health risks even in 90 degree temperatures. Scientists now believe that human-caused climate change is having an undeniable effect on almost all contemporary heat waves, making them both more severe and more frequent. As soils dry out and ambient air warms each year, heat waves like the one that rocked the Southwest this week are becoming tens or even hundreds of times more likely.
