A dangerous heat wave is shifting into the Interstate 95 corridor, placing more than 160 million people under major or extreme heat risk through the end of the week, according to the National Weather Service. Temperatures from Washington, D.C., to Boston are forecast to reach the upper 90s and low 100s, with humidity driving “feels like” temperatures to 110 degrees or higher.
Why this heat wave poses significant risks
The National Weather Service warns that current heat risk levels are associated with a sharp increase in heat-related illnesses, particularly because the current weather pattern offers little overnight relief. High humidity prevents sweat from evaporating efficiently, which hinders the body’s ability to cool itself, according to weather experts.
In many urban areas, nighttime temperatures are expected to struggle to drop below 80 degrees. Without cooler nights, the human body has little opportunity to recover before the next day of dangerous heat begins.
The upcoming heat in Washington, D.C., could make this week the hottest three-day stretch in the capital since 1930. Forecasts indicate the July Fourth holiday there could reach 102 degrees, surpassing the record of 100 degrees set in 1919.
How cities are responding to the emergency
Major cities across the East Coast have activated emergency response plans to protect residents and visitors. Philadelphia has declared a Heat Health Emergency through Saturday evening, shortening its July 4 parade route and moving a ceremony featuring a live virtual address from the pope indoors. The city has also reduced hours for the city’s World Cup Fan Festival ahead of Saturday’s match between Paraguay and France.
Washington, D.C., has activated an Extreme Heat Alert through July 5. Organizers of National Mall celebrations are deploying air-conditioned buses, cooling tents, and extra water stations to support the hundreds of thousands of visitors expected in the city.
New York City is opening hundreds of cooling centers and deploying mobile medical vans to provide water, sunscreen, and wellness checks. Officials have arranged for more than 2,200 LinkNYC kiosks to display directions to the nearest available cooling center.
The federal government’s move to issue emergency energy orders reflects the high stakes of this weather event. By increasing electricity generation within the PJM Interconnection grid, authorities are attempting to mitigate the risk of power outages that often accompany the extreme strain of prolonged heat waves.
What happens next
The heat wave is expected to persist through the end of the week, with dozens of long-standing temperature records likely to be broken. If New York City reaches a heat index of 110 degrees on Thursday, it would join only three other days since records began in 1943 with a heat index that high.
Relief is expected to arrive in parts of the Midwest later in the holiday weekend before gradually spreading into the Northeast. However, much of the South is likely to remain hotter than normal into next week.
Frequently Asked Questions
What is causing this heat wave?
The heat waves are triggered by intense heat domes—areas of high pressure that lock hot air in place—which experts say are supercharged by global warming.
Are there specific risks for the Mid-Atlantic region?
Yes, the Department of Energy has issued emergency orders to increase electricity generation in the PJM Interconnection grid to reduce the risk of power outages.
How does this compare to past heat waves?
In eastern Virginia, the current event could be the most significant heat wave since July 2012, which resulted in a dozen deaths in the state, among the more than 30 heat-related fatalities across four states.
How are you adjusting your outdoor plans to account for these extreme temperatures?
