LOUISVILLE, Ky. (WDRB) -- Concerns about security are in the background as crews make final preparations for Thunder Over Louisville.

The biggest obstacle today was the weather as crews work to make Thunder both fun and safe.

Despite the cold and wind, Zambelli crews are busy on the Second Street Bridge loading the 50-thousand shells; some 25 tons of explosives.

The bridge was shut down yesterday, but Zambelli has been in town for a week preparing to blow up the largest fireworks show in North America.

"It's an ongoing process that really won't be complete until tomorrow morning. We just want to make sure we don't put things out too early in weather conditions that are suspect at this point. But we'll be ready for tomorrow night's show," said Michael Richards of Zambelli Fireworks.

In the main control room, high atop the Galt House, it's what's called "Gear Up Day."  The computers that control the show are all in place. Now it's a matter of connecting them together and double-and-triple-checking the signal.

"Once that's in the place, we'll just start loading the program into the final computer that's going to run the show and off we go," said Thunder producer Wayne Hettinger.

But everywhere in the background, there are still concerns about security.  More than 1,000 officers will be on patrol, but police are calling on Thunder patrons to keep track of their belongings.

"Especially leaving like coolers and backpacks around where it heightens people's fears. We ask that you keep up with that the best you can," said LMPD spokesman Dwight Mitchell.

And heightened security stretches even into the river.  "There's the possibility of threats, and the Coast Guard will be patrolling, along with our partners. But we really put the onus on the public to keep an eye out for anything. Be alert. And if you do see anything suspicious, please report it," said Lt. Jeff Albe of the U.S. Coast Guard.

For the vendors, the main concern is not security, but sales.  Nathan Miller of Old Kentucky Kettle Corn is hoping for a break in the weather.  "Kettle Corn is usually not affect by weather. We sell it at 34 degrees or we can sell it at 70 or 80. Lemonade, yes. We definitely want the temperature to be just right."

There have been some changes to the street closing schedule because of a concert at the YUM Center and the Bats baseball game.

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