Charles Rex Arbogast, AP
Daredevil Nik Wallenda, responds to a question during a news conference Friday, Oct. 31, 2014, in Chicago. On Sunday, Wallenda will attempt to walk uphill at a 15-degree angle from the Marina City west tower across the Chicago River to the top of the 635-foot Leo Burnett Building. (AP Photo/Charles Rex Arbogast)

CHICAGO — The tightrope is waiting for Nik Wallenda in Chicago.

The 35-year-old high-wire artist — great-grandson of Karl Wallenda of the famous Flying Wallendas circus family — plans to perform two nail-biting walks, without a net or harness, that will be televised Sunday to millions of viewers around the world.

The Discovery Channel will use a 10-second delay for the broadcast, allowing producers to cut away if Wallenda falls.

The daredevil's challenge starts just after sunset when the skyscrapers up and down the Chicago River will be lit up and sparkling. First, he will walk uphill at a 19-degree angle from the Marina City west tower to the top of a skyscraper on the other side of the river. Next, he'll walk blindfolded between the two Marina City towers — Chicago landmarks with Hollywood credits.

At around 6:40 p.m., just minutes before the anticipated start of his high-wire feat, Wallenda, who has been preparing in Florida, said the chilly conditions in Chicago would not stall him.

"Yes there's some wind, yes it's cool, but it's not unbearable," he said.

Months of preparations have meant helicopters lifting cable to the rooftops, road closures and clearances from the Federal Aviation Administration and U.S. Coast Guard. Residents of Marina City have been asked not to use laser pointers, camera flashes or drones that could interfere. Even grilling has been prohibited.

Meanwhile, Wallenda has practiced the walk in Florida. Two of his previous televised tightrope walks — over the brink of Niagara Falls in 2012 and across the Little Colorado River Gorge in 2013 — drew about 13 million viewers each.

The Discovery Channel hopes to capture an elusive real-time audience in the DVR era. The network plans to keep the almost-live telecast of Wallenda's progress on viewers' TV screens even during the commercials, using a "double box" that will show advertisements and Wallenda simultaneously.

The Marina City towers have been on screens — Steve McQueen chased a fugitive around the west tower's corkscrew parking ramp in "The Hunter" — and graced the album cover of Wilco's 2002 "Yankee Hotel Foxtrot."

Hours before the tightrope walk, Scott Jensen of Schaumburg, a Chicago suburb, waited to watch the spectacle with his 15-year-old son, Matthew, and Matthew's friend Tommy Demaret, also 15. They were bundled up and eating sandwiches while seated on a concrete planter with a nearly straight-overhead view of the high wire.

"I think anybody who does something like this is crazy and it's a once-in-a-lifetime opportunity to see it," Scott Jensen said.

Cynthia Garner traveled 90 miles from Belvidere, Illinois, with her husband Johnny.

"I'm scared of heights," Garner said looking up at the wire.

"The feeling I feel when I look up there is scared for his life," she said. "I'm scared for his life."

Journalists covering Sunday's event signed waivers relinquishing their right to claim emotional distress if they witness a catastrophe.

A year before Wallenda was born, his great-grandfather fell to his death during a tightrope stunt in Puerto Rico. He was 73.

Wallenda says after Chicago he wants to recreate a 1,200-foot-long high-wire walk made famous by his great-grandfather. Karl Wallenda's stunt at Tallulah Falls Gorge in Georgia included two headstands on the high wire.

"Life is on the wire," Karl Wallenda once said. "Everything else is just waiting."