What is a heat dome? The US heatwave explained | Weather News
Intense Heatwave Expected Across Central and Eastern U.S.
A significant heatwave is forecasted to envelop much of the central and eastern United States this week as a high-pressure system, commonly referred to as a “heat dome,” settles over the region. This phenomenon is expected to bring oppressively high temperatures and humidity just ahead of the Fourth of July weekend and the FIFA World Cup matches scheduled in several U.S. cities.
Meteorologists predict that temperatures in some areas could feel as hot as 46 degrees Celsius (115 degrees Fahrenheit). The National Weather Service (NWS) has warned that numerous temperature records might be shattered, designating the conditions as “dangerous.” Currently, over 60 million people are under heat alerts.
Understanding Heat Domes
A heat dome is characterized by a significant area of high pressure that traps warm air close to the ground, acting like a lid over the atmosphere. As the air sinks, it compresses and warms, preventing cooler air and storms from entering, thus facilitating prolonged periods of excessive heat.
These heat domes are often linked to extended heatwaves that can last several days.
Duration of the Heatwave
The heat dome is already forming and is expected to intensify over the coming days, moving from the central U.S. towards the East Coast. Meteorologists anticipate the hottest conditions will prevail Thursday and Friday, continuing into the Fourth of July weekend. Some regions, particularly across the Great Plains, Southeast, and Mid-Atlantic, may experience unusually elevated temperatures into the following weekend.
Projected High Temperatures
Daytime temperatures are expected to reach the high 30s Celsius (low 100s Fahrenheit) across much of the affected areas. However, humidity may elevate heat index values, making it feel between 40 and 46 degrees Celsius (100 and 115 degrees Fahrenheit).
“This heat is impactful for everyone, not just vulnerable populations,” said NWS meteorologist Bryan Putnam. The evenings are unlikely to provide significant relief, with overnight lows remaining in the 20s Celsius (70s Fahrenheit).
Areas Most Affected
The most severe conditions are anticipated in a wide corridor stretching from the Great Lakes to the East Coast. Major cities such as New York, Philadelphia, Washington, and Chicago are likely to record their hottest days of the year.
Philadelphia, which is set to host FIFA World Cup events, has altered Fan Festival hours to accommodate the heat.
As temperatures rise, cities across the nation are implementing emergency measures. In Chicago, cooling centers will be opened, and city officials will check on vulnerable residents. New York City is deploying hydration vans and pop-up cooling stations equipped with misting fans.
In Washington, D.C., where temperatures are predicted to exceed 38 degrees Celsius (100 degrees Fahrenheit), the heat will coincide with Fourth of July celebrations, including what organizers promise will be the largest fireworks display on the National Mall.
Staying Safe in the Heat
The NWS advises residents to stay hydrated, limit outdoor activities during the hottest hours, and seek air conditioning or cooling centers. When outdoors, individuals should wear loose clothing and seek shaded areas.
Experts highlight the risks associated with prolonged heat exposure, particularly when the body lacks adequate time to cool down overnight. They recommend drinking water proactively and limiting alcohol consumption to reduce the risk of dehydration.
Geoff Cornish, assistant chief video meteorologist at AccuWeather, emphasizes the importance of recognizing signs of heat-related illness, advising individuals to seek cooling measures at the first signs of dizziness or lack of sweating and to seek medical attention if severe symptoms arise.