The "Salute to America 250 Celebration & Fireworks" celebration in Washington, D.C., is being evacuated Saturday due to thunderstorms moving into the city.

The event was set to begin at 7 p.m., but the program has been delayed and attendees were asked to temporarily leave and seek shelter in nearby buildings.

President Donald Trump is scheduled to participate in the event with a rally and speech before fireworks.

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On Saturday night, after a special edition of "World News Tonight," ABC will host the Star-Spangled Bash in Nashville, featuring performances from artists including Reba McEntire, Nick Jonas, Boyz II Men, Tim McGraw, Brothers Osborne and Lauren Daigle.

Hundreds of thousands of people are expected to gather in downtown Nashville for the bash, which is hosted by Ryan Seacrest and airs at 8 p.m. ET.

The event will also feature one of the largest fireworks and drone shows in the U.S., set to a live score by the Nashville Symphony.

Washington, D.C., is preparing for its largest fireworks display ever held on the National Mall Saturday night.

The fireworks are expected to begin between 10:30 and 11 p.m. and will launch from 10 sites around the National Monument, officials told ABC News. The show is expected to last approximately 35 minutes.

Officials said the secured viewing area on the Washington Monument grounds has a capacity of approximately 150,000 people and is expected to fill early.

The Secret Service is coordinating the broader security operation for the celebration, which has been designated as a National Special Security Event, bringing extensive coordinated federal, state and local security resources to D.C.

“While we are confident in our planning, we recognize that we are in a heightened threat environment,” Secret Service Special Agent in Charge of the Washington Field Office Tara McLeese said.

“This weekend, hundreds of federal agents and officers, including Secret Service specialized tactical units, counter drone teams, National Guard members, and a variety of additional unseen resources will be used to disrupt any bad actor,” McLeese said.

-ABC News’ Beatrice Peterson

The Coast Guard is surging resources to help secure July 4 celebrations in Washington, D.C., and around the country, the head of the agency said.

"We've surged over 1,000 additional people, in addition to our regular Coast Guard forces, 79 boats to 13 cities to make sure we are prepared for any contingency, and we can prevent or respond to any threat," Adm. Kevin Lunday, commandant of the Coast Guard told ABC News' Chief Justice Correspondent Pierre Thomas.

For the first time, a large swath of the Potomac around the D.C. monuments will be closed to boaters to make way for a larger than normal fireworks display on the Fourth.

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