The fireworks are set to begin at 11 over the Benjamin Franklin Parkway.

Last year, with the threat of rain and lightning, those gathered on the Parkway waiting for the display were told to go home because the 10:45 p.m. show was canceled. About 40 minutes later, after the crowd dispersed, the fireworks began.

This year, the fireworks are set to begin after the R&B singer John Legend ends his set and leaves the stage.

But once again, the forecast threatens showers and thunderstorms, which could last throughout the weekend.

"Rain won't stop us," Johnson said. "The only thing that will delay the fireworks is if the weather is severe."

And if that happens, Johnson promised to put the public announcement system to good use.

The Sunoco Sweet Sounds of Liberty Concert and Fireworks begins at 8:30 in front of the Philadelphia Museum of Art with the sounds of Philly's own Russell Tompkins Jr. and the New Stylistics, followed by Legend and ending in fireworks.

The theme of the fireworks display is "The Melting Pot, USA," a journey that begins with America's founding, followed by music and colors from nations around the world. The show ends with a new song by Philly diva Patti LaBelle titled "I Am an American."

There will be thousands of fireworks, handled by Zambelli Fireworks Internationale. New displays include the Zambelli special, which breaks like a comet and has brilliant shades of blue and purple.

"It's going to be an awesome display," said George Zambelli, 60, who started in his grandfather's business at age 12.

The celebration will continue on Saturday with a concert and festival at Penn's Landing featuring food, ice cream, Boyz II Men and more fireworks.