US President Donald Trump is set to headline the United States' 250th Independence Day celebrations on Saturday with what he has described as a "spectacular rally" at the National Mall in Washington, D.C.
The flagship event, officially titled the Salute to America 250 Celebrations & Fireworks, will feature military flyovers, live performances and what organisers hope will be the largest fireworks display in the country's history.
Military aircraft are scheduled to fly over Washington every hour from 1:15 p.m. local time until sunset, with Trump's new Air Force One expected to be part of one of the aerial formations.
Trump is expected to address the gathering at around 9:45 p.m. local time and has said he plans to deliver a "really long speech" despite soaring temperatures, adding that he wants "to show that I can do anything."
However, the celebrations are taking place under challenging conditions. Much of the eastern and central United States remains in the grip of an intense heatwave, with temperatures expected to reach around 38 degrees Celsius (100 degrees Fahrenheit). Forecasters have also warned of possible evening thunderstorms, raising concerns about disruptions to the outdoor programme.
The extreme weather has already forced the cancellation of several events scheduled earlier in the day, while the later-than-usual start time and humid conditions could also affect attendance.
The White House-backed public-private partnership organising the celebrations has nevertheless proceeded with the event, describing it as a landmark tribute to America's 250-year history.
The celebrations have also drawn political criticism.
Opponents have accused Trump of politicising what is traditionally viewed as a non-partisan national celebration, while several musical performers reportedly withdrew from the event shortly after being announced.
Ahead of the festivities, Trump used a speech at Mount Rushmore National Memorial in South Dakota on Friday to argue that American identity is under threat from what he described as domestic "radicals" and "extremists."
He also warned of what he called a resurgence of the "communist menace" and criticised "newcomers" whom he said embraced ideas contrary to the American way of life.
The remarks reflect an increasingly aggressive campaign message ahead of the November midterm elections, with Republicans seeking to portray Democrats as aligned with socialist and communist ideologies.
Despite the political backdrop and challenging weather conditions, the Independence Day celebrations are expected to draw thousands of people to the National Mall for one of the largest commemorative events marking the nation's 250th anniversary.
The Fourth of July fireworks display is an annual tradition in Washington DC and Trump has promised that this year's version - which is scheduled to begin after his remarks - would be the "largest fireworks show in history".
Approximately 850,000 fireworks will be launched from 10 sites across the city, including eight barges on the Potomac River, according to the event's organisers. It is expected to last for 40 minutes - twice as long as the usual display, which features about 20,000 fireworks.
