Millions of people in the U.S. celebrated and suffered under heat warnings Thursday as they flocked to beaches and traveled in droves to toast their nation’s birth with July Fourth parades, cookouts and the always anticipated fiery splashes of color in the evening sky.

In Washington, neon bursts of light illuminated the night above the National Mall. The Boston Pops performed a musical fireworks spectacular at that city’s Hatch Memorial Shell. And at parades all across the country, from Brattleboro, Vermont, to Waco, Texas, to Alameda, California, revelers dressed up in red, white and blue and waved the Stars and Stripes in commemoration of Independence Day.

Travel records were projected to fall with people jamming airports and crowding highways to reach Fourth of July celebrations that will stretch into a long weekend for many.

On the East Coast, some would-be beachgoers in Connecticut were turned away as parking at state parks filled to capacity, including a 2-mile (3 kilometer) stretch at Hammonasset Beach State Park, the state's largest shoreline beach.

Across the West, meanwhile, residents dealt with stifling heat as the National Weather Service warned of a “significant and extremely dangerous” heat wave across much of the region. Some spots in the desert Southwest were expecting temperatures topping 120 degrees Fahrenheit (49 degrees Celsius), and hot, muggy conditions also permeated the Deep South and Middle Atlantic.

A heat advisory in Philadelphia that came with temperatures tipping into the 90s didn’t stop crowds from gathering at historic sites in the city where the Declaration of Independence was adopted on July 4, 1776.

Outside the National Constitution Center, volunteer actors dressed in Revolutionary War-era costume made of heavy wool, despite the heat. Participants said it was worth it.

“It keeps you connected to your neighborhood and where you live,” said Adrian Mercado, who donned a 6th Pennsylvania Regiment uniform.

Evening fireworks were scheduled over the Benjamin Franklin Parkway, after a concert by Ne-Yo and Kesha.

In New York City, Macy’s annual fireworks show fired off thousands of projectiles from the Hudson River, lighting up the skylines of Manhattan, Hoboken, and Jersey City.

From Queens, bright golden and orange exploding orbs could be seen silhouetting the Empire State Building, itself lit up in red, white and blue. Mild weather brought residents to their rooftops, where many lit their own fireworks.

“This is how we celebrate. It’s the bombs bursting in air. It’s the rockets’ red glare. That’s how people show their pride and patriotism,” said Julie Heckman of the American Pyrotechnics Association.

All signs pointed to big celebrations: The Transportation Security Administration reported that a record of nearly 3 million people traveled through airports in a single day last week, a figure expected to be broken this week. AAA projected that 60.6 million people will travel by car during the holiday period. Part of the boost was attributed to easing inflation, though many Americans remain concerned about the economy.

In suburban Chicago, Highland Park resumed its annual parade on the second anniversary of a mass shooting that took seven lives and injured dozens at the 2022 event. Residents gathered at a middle school for a remembrance before the parade, which followed a different route than in the past.

“July Fourth is always going to be a day of mixed emotion,” Mayor Nancy Rotering said. “We come forth today hoping we as a community can remember and honor the lives lost.”

The holiday celebrating the establishment of a new country free from British rule is traditionally marked by barbecue, cold drinks and the Stars and Stripes on flagpoles and on clothing, in addition to the parades. But some were also celebrating in other ways unique to their communities.

Of course there was the annual hot dog eating contest on New York’s Coney Island, where a new champion chomper emerged: Patrick Bertoletti of Chicago gobbled down 58 hot dogs to win his first men’s title. In the women's competition, Miki Sudo of Florida downed 51 links to notch her 10th title and set a new record.

In Alaska, the city of Seward got a head start with a fireworks display at midnight, as thousands of people gathered on a rocky beach during the brief window when the sky dims this time of year in the land of the midnight sun. The shells burst over Resurrection Bay as people watched in silence. “It was absolutely magical,” resident Iris Woolfolk said.

The Northern California city of Oroville’s annual fireworks were canceled due to a wildfire, although most of the 17,000 people under evacuation orders or warnings were able to go home as hundreds of firefighters toiled under extreme heat.

The July Fourth holiday generally unites Americans in their shared love of country, but the 2024 version comes against a backdrop of deep political polarization and a divisive presidential race.

In Boston, where tens of thousands were expected to enjoy the Boston Pops Fireworks Spectacular, conductor Keith Lockhart said it’s inspiring to see people of different political stripes gather on Charles River Esplanade.

But, he noted, “one would have to have one’s head pretty deeply stuck in the sand to not notice the deep divisions in our country.”

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Associated Press writers John O'Connor in Springfield, Illinois; Isabella O'Malley in Philadelphia; Susan Haigh in Hartford, Connecticut; and Morgan Lee in Santa Fe, New Mexico, contributed to this report.