The United States of America marked its 250th birthday with fireworks, flyovers, some intense weather across the country, much of which has broiled under an unforgiving heat wave for days.

"The American dream is back," US President Donald Trump told a cheering crowd at a delayed rally on the National Mall in Washington before the reputed largest fireworks display ever in the US lit up the night.

The 4 July federal holiday commemorates the 13 US colonies signing the Declaration of Independence in 1776 to end British rule.

The sharply divided country has seen Trump criticised for making himself central to the milestone and politicising it by launching Freedom 250 celebrations, which are separate from congressionally established America 250 events.

Trump's remarks - where he hit on recent political themes of rejecting communism, Save America Act legislation he favors and the right to bear arms - wrapped up just before midnight at the Freedom 250 event.

Upon closing, he told the crowd, "this is only the dawn of the golden age of America" with its destiny "written by God".

The celebration, which included a flyover - one featuring the new Air Force One jet - a concert, and fireworks as well as the speech was delayed by a thunderstorm that forced an evacuation of the National Mall in the early evening.

 power in the east due to extreme weather with another 150,000 in New Jersey, according to tracker Power Outage.

Energy company DTE said that severe weather, including winds over 60mph (97kmph) on Friday evening in Michigan, left more than 350,000 homes in the state without power.

Other states affected include Pennsylvania, Illinois, Ohio, New York and Wisconsin.

Former presidents reflect

All four living former US presidents also shared messages to celebrate the milestone. President Joe Biden, Trump's predecessor, recalled the Declaration's edict that Independence that all people are created equal.

"We chose that path 250 years ago but that's where the work began, not where it ended," he said before warning that the nation's promise of equality for all was still a work in progress.

The country's first black president, Barack Obama, reshared excerpts of a recent speech he made at his presidential museum's opening.

"There's more to do to fulfil the nation's founding ideals," he said. "Every generation must take up the unfinished work of the last and carry it further - protecting what's right, fixing what's wrong, and making our union a little more perfect."

The 43rd president George W Bush said "the next 250 years require Americans to be citizens, not spectators".

Americans need to "take an active interest in the health and welfare of our country and the communities in which they live", he said.

His predecessor Bill Clinton took a moment to comment on US politics today.

"Today, we celebrate this milestone amid another period of deep division, renewed questions about America's future and role in the world, and serious threats to our own institutions and to our democracy itself," the 42nd president said.