“In light of current heat conditions, Freedom 250, United States Park Police, National Park Service, the United States Secret Service, and the Federal Emergency Management Agency have coordinated closely to adjust event timing and expand cooling resources, water stations and medical support across the grounds.”
If the forecasts are correct, the nation’s capital is on course for the hottest July 4 since 1919.
Other precautions include extra hydration stations and medical facilities.
Visitors have been urged to take breaks from the sun, make the most of air-conditioned pavilions and seek shade.
Other precautions include wearing loose clothing and wide-brimmed hats.
It is the latest challenge for an event that has been dogged by controversy.
Critics have accused Freedom 250, the public-private partnership running the festivities, of being too close to Trump’s Maga movement.
Organisers are pressing ahead with a planned concert on Friday night. But the Capitol Police will not open the gates to the public until 7pm.
“To ensure a safe concert, all guests are strongly encouraged to bring an ample supply of water to stay hydrated,” Capitol Police said.
Non-glass water bottles and coolers are allowed, they added.
The concert, which has been a July 4 tradition for more than 40 years, was held a day early to accommodate the festivities on Saturday.
In another break from tradition, the public is not allowed to attend the rehearsal on the eve of the performance.
The concert, which will be held on the West Lawn of the US Capitol, will include appearances by Patti LaBelle, Alan Jackson, Chicago, Kool & the Gang as well as the National Symphony Orchestra, and the US Army Band Pershing’s Own.
More celebrated artists who were set to appear pulled out after discovering it was aligned with Trump’s Maga movement.
Those pulling out included Morris Day, the Time, Young MC, Martina McBride, the Commodores and Bret Michaels.
The heatwave is the latest misfortune to befall what Trump had billed as “the most spectacular birthday party the world has ever seen”.
Attendance at the Great American State Fair has also been disputed, with many observers saying that Trump’s estimate of 45,000 on the first day was a gross overestimate.
NBC put the figure at “more than 1000”. Ten states boycotted the event.
There were also reports that part of the stage for the Freedom 250 event collapsed during a rehearsal.
Emergency services have scrambled to put in extra hydration centres on the State Fair site, and some booths have complained of failing air-conditioning systems.
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