WASHINGTON - A dangerous heat wave upended Fourth of July celebrations across swaths of the central and eastern U.S. on Friday, forcing officials in the nation's capital and elsewhere to cancel or postpone dozens of parades, concerts and fireworks displays.

Among the events disrupted by the sweltering heat was the Great American State Fair on the National Mall in Washington, a centerpiece of President Donald Trump's efforts to mark the nation's 250th birthday.

The fair, designed to showcase all 50 states, was temporarily closed on Friday afternoon as temperatures reached 101 degrees Fahrenheit (38 degrees Celsius). Local media said the event later reopened.

Record-breaking temperatures spread to the eastern U.S. from the Midwest earlier this week due to the emergence of a high-pressure system known as a "heat dome," which traps a mass of hot air over a region and can cause humidity to spike.

The scorching conditions also strained power grids. PJM, the largest U.S. power grid operator serving 67 million people in the ⁠Mid-Atlantic, South and Washington, D.C., areas, ordered customers enrolled in emergency conservation programs to curb usage. The steps were needed to battle generator outages, overloaded transmission lines and a surge in air-conditioning demand due to the heat.

In New York, Con Edison said roughly 17,000 customers were without power as of late Friday afternoon. As demand surged, it urged customers in New York City and Westchester County to conserve electricity.

In New York City, shoe soles stuck to Manhattan streets as adhesives softened in the heat. The city's extreme heat warning did not stop fans from gathering on sweltering sidewalks to watch celebrity guests arrive at Madison Square Garden for what was widely expected to be the wedding celebration of pop megastar Taylor Swift and football hero Travis Kelce.

A worker waved SUVs carrying guests into the venue while holding a water bottle in one hand and a towel to wipe sweat from his face in the other.

Over 185 million people, more than half the U.S. population, were under heat alerts on Friday, the National Weather Service said. Peak heat indexes could reach 115 F (46 C) in parts of the country, with several cities setting record temperature highs.

Forecasters and government officials have warned that the heat wave could prove deadly. They urged Americans spending the long weekend outdoors to stay hydrated, seek shade and watch for signs of heat illness at gatherings and public events.

Event cancellations were reported across the Eastern Seaboard for the July 4 weekend, when Americans typically gather for barbecues, parades and fireworks displays to celebrate the nation's 1776 Declaration of Independence from Britain.

In Philadelphia, officials canceled the Salute to Independence Parade, a marquee event in the city's semiquincentennial celebrations, citing extreme heat. The decision came after temperatures hit 103 F on Thursday, tying a record high last seen in 1901.

Elsewhere, heat-related disruptions rippled across the region. Haddon Township, New Jersey, canceled its annual July 4 parade. Watertown in upstate New York called off its Independence Day concert and fireworks display. In Boston, officials delayed entry to an annual riverside fireworks celebration by four hours, to 4 p.m. instead of noon.

(Reporting by Ahmed Aboulenein in Washington, Nathan Layne and Maria Tsvetkova in New York, Lisa Baertlein in Los Angeles and Tim McLaughlin in Boston; Editing by Donna Bryson, Mark Porter and David Gregorio)

A person descending the stairs of the Lincoln Memorial covers her face with her hand amid a heatwave in Washington, D.C., U.S., July 1, 2026. REUTERS/Annabelle Gordon Annabelle Gordon Reuters

Tourists use an umbrella to block the sun as excessive heat hits Washington, D.C., U.S., July 1, 2026. REUTERS/Annabelle Gordon Annabelle Gordon Reuters

Visitors of the Lincoln Memorial fan themselves amid a heatwave in Washington, D.C., U.S., July 1, 2026. REUTERS/Annabelle Gordon Annabelle Gordon Reuters

A girl splashes water onto herself at the World War II Memorial amid a heatwave in Washington, D.C., U.S., July 1, 2026. REUTERS/Annabelle Gordon Annabelle Gordon Reuters

A woman sits in the shade and fans herself at the base of the Washington Monument due to excessive heat in Washington, D.C., U.S., July 1, 2026. REUTERS/Annabelle Gordon Annabelle Gordon Reuters

A man lies down under trees as excessive heat hits Washington, D.C., U.S., July 1, 2026. REUTERS/Annabelle Gordon Annabelle Gordon Reuters

Copyright Reuters or USA Today Network via Reuters Connect.

This story was originally published July 3, 2026 at 7:30 PM.

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