They came early, they came often, and they came ready to celebrate Independence Day with the Pops, if not the pyrotechnic bangs.

More than a dozen eager spectators had lined up at the gates of the Charles River ­Esplanade’s Hatch Shell by noon Tuesday to ensure their front-row seats for the Boston Pops orchestra rehearsal of their signature July Fourth concert more than eight hours away.

The real show will be Wednesday, when more than 10,000 fireworks are launched as part of the legendary show over the Esplanade.

That is, if Mother Nature cooperates. The National Weather Service is predicting thunderstorms through the day, with clear skies during the evening. Temperatures are ­expected to be in the low 80s.

Rain, event officials say, will not deter the 10:30 p.m. show. Lightning, however, could cause major problems. A lightning storm would endanger revelers and require staff to evacuate the fireworks barges, officials have said.

Rain will not deter the 10:30 p.m. show. Lightning, however, could cause major problems, endangering revelers and requiring staff to evacuate the fireworks barges.

“We will consult with our weather forecasters and a team of public safety officials before any decision [about canceling the show] is made,” said Steve MacDonald, spokesman for Boston 4th Productions.

He said that lightning and strong winds would force a cancellation, but light rain would not stop the 20-minute fireworks show.

A rainy Wednesday would be a departure from the otherwise nice weather for the build-up to July Fourth and for another big Boston attraction, Operation Sail 2012, the tall ships showcase.

“It’s really been a beautiful week,” said Dominic Amenta, an Operation Sail spokesman, who said the tall ships display is on pace to attract about 800,000 visitors. The event, which opened Saturday and runs through Thursday, is part of the city’s celebration of the bicentennial of the War of 1812.

“We’re attracting a ton of people from throughout New England,” Amenta said. “There are people from all over. Yesterday we ran into a family that came up from Pennsylvania.”

The commute was a little shorter for Massachusetts ­natives ­Andrew Ley and Carol Searle, who could almost point out their home in the Financial District from the end of the Charlestown Navy Yard pier.

“We were here Saturday, we were here yesterday, we’re here today, and we’ll be here tomorrow,” said Searle, who said seeing the ships conjured memories of visiting the USS Constitution as a child.

The pair were far from the only locals out at the Navy Yard, which is hosting three of the 14 tall ships.

On Tuesday afternoon, most in the crowd were wearing ­either a Boston College shirt or Red Sox cap.

“I’d bet most Bostonians have been to the USS Constitution once, when they were 7,” Ley, 67, said. “This is a great ­excuse for them to come back out and see it again.”

The mood was more patriotic on the Esplanade. Dressed in varying amounts of red, white, and blue, dedicated Fourth fans napped, read, snacked, and chatted for hours as crews tested microphones, lights, and monitors in preparation for the the rehearsal.

The show featured the ­Boston Pops, Dropkick ­Murphys, and Jennifer ­Hudson, but no fireworks.

“It’s America’s birthday, and we’re honored to have the Pops perform here for us for free,” said Bolton resident Maryann Rollings, who wore star-shaped sunglasses, a red, white, and blue top hat, and a sparkling wig.

Rolling’s three friends ­— one dedicated attendee and two newcomers — wore similar celebratory outfits as they passed out grapes and cookies from a cooler.

“It’s a great testament to America . . . to have such a large group of people together enjoying themselves,” Rollings said.