July 4 heat dome: Map shows states facing dangerous temperatures
A heat dome is forecast to send temperatures soaring across much of the central and eastern U.S. over the July 4 holiday, with forecasters warning that extreme heat could affect millions of Americans heading into one of the busiest outdoor weekends of the summer.
The National Weather Service’s Climate Prediction Center forecasts hotter-than-normal weather across more than 30 states from July 2 to 6, with some set to see temperatures hit the high 90s and low 100s.
The greatest chance of unusually high temperatures stretches from the Midwest into the East, including Minnesota, Wisconsin, Iowa, Illinois, Indiana, Missouri, Michigan, Ohio and Kentucky.
Above-normal temperatures are also expected across much of the South—including Tennessee, Arkansas, Mississippi, Alabama, Georgia and the Carolinas—and along much of the East Coast, from Virginia to New England.
Overnight temperatures are also expected to remain unusually warm in many areas, with lows only falling into the mid- to upper 70s, limiting relief from the daytime heat.
Only parts of the Pacific Northwest and Alaska are expected to be cooler than average, while much of the western U.S. is forecast to see temperatures closer to seasonal norms.
What Forecasters Are Warning About
The Climate Prediction Center warned that the heat could pose a significant health risk during the July 4 holiday, particularly as many Americans are expected to spend long periods outdoors.
The agency has issued a high risk of extreme heat for July 4 across parts of the eastern Great Plains, the Mississippi, Ohio and Tennessee valleys, the Appalachians, the Southeast and the Mid-Atlantic. A broader moderate risk extends from the Great Plains to the East Coast through July 5, while a slight risk covers much of the Great Basin, Rockies, Great Plains and eastern U.S. through July 7.
“Another key consideration is the Nation’s 250th Anniversary on July 4, with numerous outdoor activities planned,” the CPC said. “Staying hydrated and limiting exposure to very hot, humid weather is very important, especially vulnerable populations including older adults.”
Why a Heat Dome Is Forming
The hot weather is being driven by a large area of high atmospheric pressure—commonly known as a heat dome. As the high-pressure system strengthens, it traps hot air beneath it, allowing temperatures to build over several days while limiting cloud cover and rainfall, according to the National Weather System.
This persistent ridge of high pressure will keep temperatures well above average across much of the country through the start of next week. Combined with high humidity, the pattern is expected to push heat index values (what the temperature feels like) above 100 to 105 degrees in many areas, while unusually warm nights offer little relief, the CPC said in its hazards outlook.
Forecasters expect the ridge to gradually shift westward after July 4. That should bring some relief to parts of the East Coast later in the holiday weekend, while increasing the risk of extreme heat across portions of the interior West, including parts of the Great Basin and Rockies.
Why the Timing Matters
Besides usual annual celebrations on July 4, America is marking the nation’s 250th anniversary with major events across the country.
In Washington, D.C., a day-long celebration is planned on the National Mall, including a parade, concerts and one of the nation’s largest fireworks displays. New York Harbor will host the Sail4th 250 celebration, bringing together dozens of tall ships from around the world, while Philadelphia—the birthplace of the Declaration of Independence—will stage an expanded Wawa Welcome America festival featuring concerts, historical events and fireworks.
Communities across all 50 states are also holding parades, festivals, concerts and fireworks displays as part of the nationwide Freedom 250 celebrations, with millions of people expected to attend outdoor events over the holiday weekend.
Newsweek has broken down the details of events here.
