A dangerous heat dome is expected to bring potentially record-breaking temperatures and oppressive humidity to much of the eastern half of the United States this week, just as millions prepare for the July Fourth holiday weekend and a packed summer sports calendar.
The hottest conditions are expected to develop from the central U.S. into the East and linger into the holiday weekend, with forecasters warning that the combination of heat and humidity could make conditions feel even more severe than the thermometer suggests.
Across parts of the eastern two-thirds of the country, overnight lows are also expected to stay unusually warm, limiting relief after sunset and increasing the risk of heat-related illness for people without adequate cooling.
Players at the FIFA World Cup have already been given hydration breaks because of the high temperatures, and forecasters say the broader pattern could intensify before easing later in the week.
As per the Royal Meteorological Society, a Heat Dome is ‘created when an area of high pressure stays over the same area for days or even weeks, trapping very warm air underneath.’
It is often described as ‘a lid on a pot’.
The National Weather Service said dangerous, record-setting heat would expand across most of the central and eastern U.S. this week, with heat index values likely to top 100 degrees in many places and remain high through the Independence Day holiday weekend.
“With the combination of high humidity, heat indices may reach 100-110 Degrees,” the NWS continued.
“Much of the central and eastern U.S. is under a Moderate to Major HeatRisk, which can pose health impacts on those without hydration or cooling.”
Among the places expected to feel the impact are Washington, New York, Philadelphia and Baltimore, where temperatures could surge into the 100s.
Warnings have also been issued for central cities such as Chicago, Detroit, Kansas City and Nashville, while southern locations including Dallas and Memphis are also bracing for scorching conditions.
The Weather Prediction Center has warned that the heat is being driven by a strong ridge of high pressure aloft, a setup that can trap hot air in place for days and make temperatures climb higher with each passing afternoon.
Forecasters also say many areas will see little nighttime relief, with warm lows in the 70s and 80s in some cities, a pattern that increases the risk of dehydration, heat exhaustion and heat stroke.
According to the World Health Organization, extreme heat is a major and growing public health threat, and Europe’s current heatwave has already been linked to more than 1,300 deaths.
People in affected regions are being urged to reduce time outdoors during the hottest parts of the day, take frequent breaks in air-conditioned or shaded spaces, and check on older adults, children, neighbors and anyone without reliable cooling.
Staying hydrated is also considered essential during periods of extreme heat.
Officials also advise never leaving children or pets in vehicles, where interior temperatures can become dangerous within minutes.