SAN ANTONIO -- Miami Heat forward LeBron James was forced to exit early from Game 1 of the NBA Finals because of severe leg cramping caused by extremely warm temperatures after the air conditioning in the arena malfunctioned.

"It was the whole left leg, damn near the whole left side," James said. "I was losing a lot [of fluids] throughout the game. It was extremely hot in the building, you know, both teams, fans, everybody could feel it. I was the one that had to take the shot."

With James playing only five minutes in the fourth quarter, the San Antonio Spurs outscored the Heat 36-17 over the final 12 minutes to win 110-95 and take a 1-0 series lead.

"It was an unusual circumstance," James said. "I never played in a building like that, it's been a while, like a high school game or [youth basketball], and everybody is sitting on top and you feel good being in a building like that."

James, who could be heard telling teammates during the game that "they're trying to smoke us out of here," scored 25 points in 33 minutes before heading to the locker room.

James exited the game with 7:31 remaining in the fourth quarter because of the cramping but returned with 3:59 left for one play, finishing a driving layup. He signaled to come out immediately after, limping to the bench before having to be carried off.

James said he received intravenous fluids during the game and even changed his uniform at halftime to try to stay dry. But he couldn't prevent the onset of cramping that eventually locked up his left leg, forcing him to hobble to the bench with teammates eventually carrying him off the floor.

"It's frustration and anger, but at the same time, it's something that you try to prevent, you try to control," James said. "I mean, I got all the fluids I need to get, I do my normal routine I've done and it was inevitable for me tonight, throughout the conditions, you know, out there on the floor. I lost all the fluids that I was putting in in the last couple of days out there on the floor. It sucks not being out there for your team, especially at this point in the season."

Hall of Famer Isiah Thomas didn't begrudge James for not returning.

"There is no athlete on the planet who could've played through those cramps," Thomas told Yahoo! Sports. "Michael Jordan absolutely couldn't have played through those cramps. I absolutely couldn't have played through those cramps. As an athlete, there's nothing you could do."

A power failure for the electrical systems that run the AT&T Center left the arena without air conditioning. The Spurs Sports & Entertainment group said in a statement Friday that the air conditioning had been repaired and would continue to be monitored going into Sunday's Game 2.

With the temperature in the arena reaching as high as 90 degrees during Game 1, all players were visibly exhausted, some even putting ice packs on their necks during timeouts. Fans, who conveniently were given noisemakers that doubled as handheld fans, tried to cool themselves for the duration of the game.

LeBron James left a 110-95 Game 1 loss in the fourth quarter, needing help off the floor, presumably as a result of the conditions within the AT&T Center, which reached 90 degrees. Andy Lyons/Getty Images

"It was an unusual environment," Heat coach Erik Spoelstra said. "We're used to having the hotter arena at this time of year, but both teams had to deal with it. It's unfortunate that it was that way. It was how we responded in those minutes after that point. I think it felt like a punch in the gut when you see your leader limping like that back to the bench, but at the same time, we still had an opportunity to make plays going down the stretch, and they made obviously the biggest plays in the last five minutes."

The Spurs overcame a seven-point fourth-quarter deficit, sparked by 11 points on 4-of-4 shooting from Spurs guard Danny Green.

"I think it was probably tough on both teams," Spurs coach Gregg Popovich said. "Players were pretty dead. So we tried to get guys in and out a little bit more than we usually do. Kind of screws up the rhythm a little bit but it was mighty hot out there."

Said Spurs forward Tim Duncan: "I don't think I've played in anything like this since I left the [Virgin] Islands. It was pretty bad out there."

The uncomfortable situation affected both teams, although the Spurs were able to handle it better. Spurs guard Tony Parker noted that he often played in similar environments in Europe, and with a large part of the Spurs' roster made up of international athletes used to playing without air conditioning, that potentially contributed to their ability to respond.

"Me personally, it didn't bother me, felt like in Europe," Parker said. "Felt like I was playing in the European championship. We never have AC in Europe, so it didn't bother me at all."