San Francisco prepares for Fourth of July fireworks extravaganza

The countdown is on for the fireworks show scheduled to take place over the San Francisco Bay.

On Wednesday, crews spent the day loading the mortars and prepping for the big show.

In years past Fourth of July celebrations have lit up the skies above San Francisco and thrilled the crowds.

Crews got the barge ready for the 20 to 25-minute spectacle expected to light up the night sky.

"Yup, a lot of work," said Jeff Thomas from Pyro Spectaculars by Souza. "We have the fortune of having worked with the city for many years, so we kind of have this dialed. But, still, there's a lot of prep work."

Organizers say they like to keep the show fresh and thrill the crowd, so expect something new.

"We have a few shells that have never been seen before, we'll just keep that to ourselves. You'll see them," said Thomas.

As always, the weather is the X-factor. Showrunners say even with San Francisco's notorious fog, there's only been one show in recent memory where the show was completely obscured.

"You can have a little bit of cloud cover and still make it work," said Thomas.

Pier 39 finalized its Fourth of July lineup, announcing plans for a rock concert from 3 to 6 p.m. all leading up the fireworks extravaganza.

Expect big crowds at Pier 39.

But hopefully not on Treasure Island.

The Treasure Island Development Authority (TIDA) says a construction boom means it might not be the ideal place to watch the show.

In years past, it has been a premier spot to watch the show, but work has restricted roads and turned viewing areas into active construction sites

"It's difficult to get around the island," said Jack Nathanson with TIDA. "We lack the parking that we used to have, and also the open space for people to spread out and enjoy the fireworks show."

TIDA says work is underway to transform the area into a massive park.

Once that's done it will once again be one of the best spots to watch fireworks.