A dangerous, multi-day heat wave is intensifying its impact on the eastern United States, shattering records, straining the power grid and increasing risk for millions of people preparing to celebrate Independence Day outdoors. And human-induced climate change is making familiar summer weather patterns even more dangerous.
This heat wave was caused by a powerful heat dome lodged over the northeast. This dome is a stagnant area of high pressure that traps and intensifies hot, humid air.
But the intensity of this week’s heat and humidity would have been “virtually impossible” without the influence of fossil fuel pollution. The findings were released early Friday by World Weather Attribution, a scientific network that analyzes the role of climate change in causing extreme weather events.
🔥 Get heat forecasts with the CNN Weather app
Friederike Otto, professor of climate science at Imperial College London, said: “When a historic Independence Day celebration is interrupted and World Cup matches are played in conditions that are dangerous for players and fans, it shouldn’t take new scientific research to wake people up.” “Climate change is here, it’s already affecting what we enjoy in our daily lives, and the longer the inevitable transition to net-zero emissions drags on, the worse it will continue to get.”
The worst of the heat is set to arrive on Friday after at least 20 locations broke or tied daily temperature records on Thursday. As homes and businesses turn up their air conditioners to stay cool, demand for electricity is surging across the Mid-Atlantic and Northeast, where heat and humidity are pushing conditions into dangerous territory.
High temperatures are expected to approach or exceed 100 degrees in Washington, D.C., Philadelphia, New York City and Boston on Friday. The combination of heat and humidity will make temperatures feel even hotter, with heat index values (how the air actually feels on your body) expected to soar to 107 degrees in Washington and New York City, 110 degrees in Philadelphia, and 106 degrees in Boston.
The intense heat continues in Washington, D.C., on Saturday, with temperatures expected to stay near 103 degrees and the heat index to reach up to 108. Philadelphia has a heat index of up to 106, which could reach 101 degrees. New York City is expected to reach 97 degrees, and Boston is expected to hit a high near 95 degrees on Saturday.
The deadliest weather hazard in the United States is heat, and high humidity increases the risk, keeping temperatures elevated and preventing sweat from evaporating efficiently, making it harder for the body to cool down. Nighttime minimum temperatures are also hotter now than they were decades ago, making it difficult for people to rest and rest.
Risks can increase quickly, especially for the elderly, children, outdoor workers, and people without reliable access to air conditioning. If you’re going out for the weekend, plan to take frequent breaks indoors or at least in the shade. Drink water frequently, avoid strenuous activity, and avoid leaving children and pets in parked cars.
Energy Secretary Chris Wright this week directed data centers in the mid-Atlantic region to use backup power sources instead of using power from the public grid to provide enough power for residential air conditioning.
Wright’s order Tuesday targeted data centers and other large power customers served by PJM, the nation’s largest power grid operator. The PJM region consists of 13 states. Virginia is home to the world’s largest cluster of data centers, and its dramatic energy use has caused some mid-Atlantic states to experience severe spikes in electricity prices in recent years.
Outside of the PJM power grid, more than 19,000 Con Edison customers across the New York City metropolitan area and upstate were without power Thursday, according to the utility’s outage map. Con Edison said Thursday it would reduce voltage in parts of the Bronx and Manhattan to conserve energy while equipment is repaired, and asked customers to limit the use of air conditioners and energy-guzzling appliances.
In a post on X, Mayor Zoran Mamdani urged residents to set their air conditioners to 78 degrees and unplug household appliances to save energy and reduce the load on the grid.
Many cities, including Boston, New York, Philadelphia, Washington, D.C., and Raleigh, North Carolina, are opening cooling centers and expanding public resources as the dangerous heat subsides.
Washington, D.C., has issued a heatwave warning through July 5 and is ramping up cooling centers, hydration stations and emergency medical resources as hundreds of thousands of tourists descend on the nation’s capital for holiday events.
Organizers of the National Mall celebration are adding water stations, cooling tents and air-conditioned buses for attendees. U.S. Capitol Police announced in a news release that Thursday night’s public rehearsal for PBS’s annual “Capitol Fourth” concert was canceled due to excessive heat. Organizers are expected to announce by 10 a.m. Friday whether the concert itself will be canceled.
New York City opened hundreds of cooling centers and deployed mobile medical vans to provide water, sunscreen and health checks. More than 2,200 LinkNYC kiosks provide directions to the nearest cooling center.
Philadelphia declared a heat health emergency until Saturday evening and shortened the route of its Fourth of July parade. A live virtual speech by the pope was moved indoors, and authorities shortened the city’s World Cup fan festival ahead of Saturday’s match between Paraguay and France. Event organizers also canceled Independence Day and World Cup block parties.
Norristown, Pennsylvania, a suburb of Philadelphia, and Haddon Township, New Jersey, also canceled their Fourth of July parades due to the heat.
Scorching temperatures could also affect air travel. Delta Air Lines has issued a heat advisory for New York’s LaGuardia Airport through July 4 “as heat exacerbates operational constraints.”
Amtrak also warned that delays could occur through July 4 if intense heat in the Northeast, Southeast and Midwest forces trains to operate at reduced speeds.
Some relief supplies are expected to begin arriving in parts of the Midwest later this weekend, before gradually spreading to parts of the Northeast. However, much of the South is expected to remain warmer than average next week.
