The Sail4th 250 parade has begun in New York City which is expected to draw large crowds to the city's waterfront.

Many of the participating vessels, known as Class B tall ships, have been arriving in New York Harbor over the past several days.

Saturday's Sail4th 250 parade begun at 7 a.m. ET, with ships sailing north on the Hudson River from the Verrazzano-Narrows Bridge to the George Washington Bridge.
Leading that event is America's Tall Ship, the U.S Coast Guard Cutter Eagle.

The larger ships are anchored near Sandy Hook as sailors from 20 nations prepare to sail up the Hudson.

The event is expected to attract thousands of spectators as New York joins the nationwide celebration of the nation's semiquincentennial.

Officials say security checkpoints and screenings will be in place for designated viewing areas during Saturday's Sail4th 250 festivities along the Hudson River.

The sun has started to rise on the East Coast as America celebrates its 250th birthday on Saturday.

From Philadelphia to Boston, Washington, D.C. to Raleigh and beyond, celebrations will be taking place across the country throughout the day and over the weekend.

Millions of Americans, however, will be contending with a heatwave that is blanketing much of the country, including in Philadelphia where the Salute to Independence Semiquincentennial Parade that had been set for Friday was canceled due to the dangerous heat wave, according to Philadelphia ABC station WPVI.

Elsewhere, America's Independence Day Parade, which was scheduled for 10:30 a.m. on July 4 in downtown Washington, D.C. was cancelled by organizers late Friday evening due to the extreme heat in the District.

Russian President Vladimir Putin sent a telegram of congratulations to U.S. President Donald Trump on the occasion of the 250th anniversary of the independence of the United States.

In the letter, Putin called the emergence of the American state through the signing of the Declaration of Independence "an important milestone in world history."

"Today, Russia and the United States, as the two largest nuclear powers, bear a special responsibility for ensuring security and stability on a global scale," Putin said. "I am confident that the establishment of constructive, equal and mutually beneficial relations between Moscow and Washington meets the interests not only of our peoples, but also of the entire world community."

-ABC News' Rashid Haddou

The iconic Times Square ball in New York City will descend on a date other than New Year's Eve for the first time as part of a historic Independence Day celebration marking America's 250th birthday.
The celebration will feature eight ball drops marking midnight across every U.S. time zone and inhabited territory, beginning in Guam and the Northern Mariana Islands and ending in American Samoa, according to an announcement by the organizer, America250.
The organizer said the rolling countdown is designed to unite Americans across the country during the nation's semiquincentennial celebration.
The eight ball drops are part of the inaugural Giving 4th Broadcast Benefit Show, a live special from One Times Square in New York City.

The event also launches Giving 4th, a nationwide initiative encouraging Americans to support charitable organizations and volunteer in their communities in honor of the country's 250th birthday.
The celebration begins with the first Times Square ball drop at 10 a.m. ET on July 3, marking midnight in Guam and the Northern Mariana Islands.
The traditional 11:59 p.m. ET countdown to the ball drop at midnight in New York will serve as the centerpiece of the nationwide celebration before the countdown continues through the remaining U.S. time zones and territories.
The final ball drop is scheduled for 7 a.m. ET on July 4, marking midnight in American Samoa.
-ABC News' Shafiq Najib