BY THE OPTIMIST DAILY EDITORIAL TEAM More than 1,300 people die from extreme heat in the United States each year. The events behind the worst of those deaths usually share the same explanation: a heat dome, a ridge of high atmospheric pressure that parks itself over a region and won’t move. Two are forming right now. One is developing in the southwest; a second is building over the subtropical Atlantic. NOAA forecasters expect them to merge over the eastern United States around the Fourth of July, pushing temperatures into the 90s as far north as the Great Lakes and Minnesota, with highs in the 100s across the South and heat indexes above 110 degrees Fahrenheit from the mid-South to the central Gulf Coast. Here is how these heat domes form, and most importantly, how to prepare. What creates a heat dome? A heat dome forms when a large high-pressure system builds in the atmosphere and holds position for days or weeks. AccuWeather Meteorologist Brandon Buckingham describes it as a pressure ridge that “acts like a lid, preventing heat from escaping and blocking cloud formation, which leads to persistently high temperatures and minimal relief from the heat.” Hot air that would normally rise and disperse gets pushed back down by the high-pressure system. As it sinks, it compresses and grows hotter, putting more heat into the surface below. Without cloud cover to interrupt it, solar radiation hits the ground directly, adding to what’s already trapped. The jet stream connection The jet stream is the fast-moving band of winds that crosses the continent from west to east in a shifting, wavy pattern, and it determines whether a high-pressure system keeps moving or stalls. When the jet stream’s north-south loops grow too large, they slow. A stalled jet stream leaves a high-pressure system in place, which is how a heat dome forms and why it can linger for days. Ocean conditions matter here too. La Niña and warmer-than-usual sea surface temperatures can alter airflow in ways that help a heat dome develop. Even after the dome is established, the jet stream still controls its movement and duration. “The positioning of the jet stream often determines how long a region will suffer under the dome and whether cooler air from higher latitudes can move in,” says Buckingham. “When the jet stream shifts or weakens, the dome may expand in size or move into new areas. Relief finally arrives when the ridge of high pressure breaks down, causing the dome to dissipate quickly.” How climate change is making them worse The IPCC’s 2023 Synthesis Report concluded it is “virtually certain” that hot extremes have become more frequent and more intense across most land regions since the 1950s. Heat domes are part of that. Warmer baseline temperatures on land and ocean both make a dome’s effects worse from the start. Drought strips away soil moisture that would otherwise cool the surface through evaporation. The two problems reinforce each other once a dome settles in. “Changes in atmospheric circulation, linked to warming in the Arctic, can lead to more stagnant weather patterns that allow heat domes to persist,” says Ashley Ward, director of the Heat Policy Innovation Hub at Duke University. Arctic warming is narrowing the temperature gap between the poles and the tropics. That gap is what drives jet stream circulation, and a smaller one produces a weaker, more erratic jet stream, one that stalls more often. The 2021 Pacific Northwest heat wave showed how fast this can get away from existing models. Temperatures ran so far past historical records that scientists had to rethink how they project extreme heat in a warming climate. What heat and humidity do to the body High temperatures alone are dangerous. Add humidity, and they can kill. Sweat works by evaporation: moisture leaves the skin and takes heat with it. When air is already saturated with water vapor, that doesn’t happen efficiently, or at all. Core temperature keeps rising. Mostafijur Rahman of Tulane University, who studies extreme weather and human health, is plain about what that leads to: “Heat and humidity together pose serious health risks,” and can “result in dehydration, heat exhaustion, and potentially life-threatening heat stroke.” Older adults, children, people with chronic conditions, and outdoor workers are most exposed. Staying safe during a heat dome Knowing that these heat domes are on the way means it’s time to prepare for yourself and those around you. Stay hydrated, stay out of the heat during peak hours, and get somewhere cool. Cold showers help. So does immersing your feet and forearms in cold water, or sitting in front of a fan with a cool damp cloth on your skin. Ward is direct about what severe heat requires: “When temperatures reach certain levels outside, the only way to be safe is to seek out air conditioning.” If you don’t have it at home, that means knowing where the nearest cooling center is and when it opens. Libraries and malls work. A neighbor’s couch works. And make sure to check on the people around you. Ward’s bottom line: “Most importantly, pay attention. Seek help immediately if you show signs of heat stroke, and check on family, friends, and neighbors who are vulnerable.”   Did this solution stand out? Share it with a friend or support our mission by becoming an Emissary.The post How heat domes form, intensify, and what they do to the body first appeared on The Optimist Daily: Making Solutions the News.