Authorities suspect the heat caused the death of one fan, a 67-year-old woman from New Jersey whose body was found Wednesday afternoon inside a trailer at a Graceland campground. She had chronic health problems, but the Shelby County medical examiner's office said the heat contributed to her death.
The Memphis Fire Department says at least six other people were treated for heat-related problems, including an 8-year-old boy who was hospitalized.
Despite the promise of another furnace-like day, many fans lined up for hours, setting up chairs and umbrellas on the sidewalk to stake out their place for the candlelight vigil marking the anniversary of Elvis' death.
The procession, with fans walking mostly single-file and holding candles, filed up Graceland's long winding driveway and past Presley's grave in a small garden beside the white-columned house. Many fans carried flowers, stuffed animals and other small gifts to leave at the grave.
Tom Vigil, 42, of Denver was determined not to let the heat stop him even though he was missing part of a lung from recent surgery.
Decked out in a black Elvis-type jumpsuit, Vigil pulled an oxygen tank behind him with a breathing tube attached to his nose.
"I'm not in the best of health, but I wanted to be out here and be part of this," he said.
Mary Powell of Salinas, Kan., said she took up her post at 5 a.m. to be sure to get near the front of the line. "A lot of people would say I'm crazy, but this has to do with my love for Elvis. He did so much for his fans," Powell said.
"I don't think we've ever seen weather this hot before," Graceland tourist Hazel Dixon told Early Show meteorologist Dave Price Wednesday morning.
"We're gonna dress light, drink lots of water and wear a hat, do everything we can to stay cool," Christine Cline told Price.
The legendary entertainer, acclaimed as The King, died 30 years ago Thursday at age 42 of heart disease worsened by prescription drug abuse.
The vigil is the most popular and solemn anniversary event in a weeklong string of concerts, dances, movie screenings and other festivities put on by Graceland.
No one keeps exact figures, but the Memphis Convention and Visitors Bureau estimated up to 75,000 people would be drawn to town for the anniversary week.
Graceland draws almost 600,000 visitors a year and up to 40,000 file through the three-story white-columned house during Elvis Tribute Week.
Fans preparing for the vigil filled the souvenir shops of Graceland's sprawling tourist complex. Elvis impersonators, with karaoke accompaniment, put on a daylong show for fans packed into a large tent in a shopping center parking lot.
Workers from a Memphis hospital passed out free bottles of water and fans lining up for the vigil could take breaks to stand for a few moments in a misting tent dubbed "Kentucky Rain" after one of Presley's songs.
Abby Reeves of North Augusta, S.C., said she expected Memphis to be hot, but not quite so hot.
"We had some family here last year and they said it was only in the 90s," Reeves said.
When Presley died, his finances were in sad shape. Led by ex-wife Priscilla Presley, the estate formed Elvis Presley Enterprises, opened Graceland to the public in 1982 and solidified the legal rights to make money on Elvis' name and image.
Last year, Graceland took in $27 million in revenue, and the overall Elvis business brings in more than $40 million a year. That made him the second-highest grossing dead celebrity in 2006, behind only Nirvana's Kurt Cobain, according to Forbes magazine.