SANTA CLARA — The death of a 49ers fan at Levi’s Stadium and the huge crowds who abandoned the sunny seats for shady concourses are shining a bright light on an issue that many Niner faithful were unprepared for Sunday: the heat.

It’s no secret Santa Clara is hotter than San Francisco, but the 49ers have also traded in the bayside fog and breezes that often cooled down Candlestick Park for the beaming Santa Clara Valley sun that glistens off the new stadium’s gleaming glass suite tower. Many of the 68,000 seasoned fans who attended the first 49ers game in Santa Clara, a preseason contest on Sunday afternoon, wound up with over-heated cellphones, sweat-drenched jerseys and an uncomfortable souvenir.

“I came home super sun burnt,” said Gabe Hernandez, a 30-year-old fan from Roseville. “Me and my friend only lasted one quarter until she tapped out to get out of the beaming sun. I miss the ‘Stick.”

Joanne McPhee, a season ticket holder for two decades, is used to hot conditions — she lives in Morgan Hill. But she said “the sun was unbearable” on Sunday. Another fan, Bill Moore, Sr., called the experience of baking in the sun “miserable.”

The stands were half-empty by halftime and almost completely vacant by the end of the game, while fans in red-and-gold jerseys packed the covered concourses and air-conditioned clubs and stood in long lines for ice cream.

Though the temperature was just above 80 degrees in Santa Clara, it felt several degrees hotter in the crowded stands Sunday. Fire Department and team officials said the heat accounted for most of the 60 emergency calls at the stadium, an unusually high number for a 49ers game, and two people were taken to the emergency room.

“Many people just needed to get out of the sun,” said fire Chief Bill Kelly. “For many of them, there was a general feeling of weakness, and (they) just needed to rest and get some water.”

The most serious call came in the third quarter, when an older man in section 221 collapsed and suffered a cardiac emergency, which is usually caused by a heart attack. Santa Clara firefighters performed CPR for at least 10 minutes and took him out on a stretcher, but he was pronounced dead at a San Jose hospital.

It’s unclear if the heat contributed to his death, as the authorities declined to speculate. Dr. Cesar Molina, a cardiologist at El Camino Hospital in Mountain View and a former board member for the local American Heart Association, said it was possible, but hard to tell without knowing the man’s full medical history.

The fan was sitting in the sun-baked part of the stadium behind the visitors’ sideline and occupying a seat someone had already vacated, said Craig Love, who was sitting in front of the man.

“It was really, really hot right there, and he was just pouring sweat,” said Love, of Corte Madera, who’s been going to games since the Kezar Stadium days. “I never remember it that hot at Candlestick.”

Love, who took a cellphone video of the incident, said he saw the fan who died talking with a man in front of him for a while. Then Love turned around and saw him passed out on a neighboring seat, covered in his own vomit. Love assumed he was drunk and turned back around. The other man sitting next to Love tried shaking the passed-out fan awake, and a woman who also seemed to be in the fan’s party came by and slapped him hard on the knee and shouted at him.

Within two minutes, stadium officials were notified. They quickly laid the man out on the concrete floor and pounded his chest for a while, to no avail, as dozens of onlookers gathered around and the game continued in the background. The man, who has not been identified, turned over and made a brief sound before paramedics arrived but was otherwise unconscious, Love said.

The 49ers, who huddled on Monday to asses the operations from the $1.3 billion Santa Clara stadium’s NFL opening, are reviewing whether to make changes to help heat-stricken fans but have not nailed down any specifics yet.

The next 49ers home game is a preseason tilt at 1 p.m. Sunday. The regular-season opener, on Sept. 14, should be cooler and starts at 5:30 p.m. There are only two other afternoon events scheduled at the stadium, both 49ers home games, before November.

The team, acknowledging this issue, is mostly pushing for better education of fans, advising them to treat a trip to Levi’s Stadium like a voyage to the beach: bring sun block and a hat, stay hydrated, monitor your alcohol content and go for a break in the shady concourses if you feel overwhelmed by the sun.

“We want to continue to work with our fans to educate them with not just the stadium, but everything that goes into enjoying the game there. The weather is obviously a part of that,” team spokesman Bob Lange said.

The stadium has three first-aid stands, and the team asks fans to text “SUPPORT” and a short message to 69050 to alert officials to medical problems.

Kelly said his crews, which include 40 first-aid personnel and 14 firefighters, will also try to get better acclimated to the kinds of issues that will crop up on game days.

“We’ll be watching for patterns,” Kelly said.

Staff writer Robert Salonga contributed to this report. Contact Mike Rosenberg at 408-920-5705. Follow him at Twitter.com/RosenbergMerc.