By Steve Keating

DALLAS (Reuters) - Sun, security and missing seats welcome thousands of Green Bay Packers and Pittsburgh Steelers fans as they poured into Cowboys Stadium for Super Bowl XLV on Sunday.

The sleet, ice and bitter cold that had threatened to derail the Super Bowl party disappeared as more seasonal temperatures returned to North Texas, bringing with them the festive atmosphere that had been missing during the game's frost-bitten buildup.

But not everyone was in a party mood, particularly the fans who arrived to find workers scrambling to install temporary seating. Approximately 850 fans were affected and were relocated to similar or better seats.

The NFL said that 400 fans in other sections could not be accommodated with seats inside the stadium and would each receive a refund of triple the cost of the face value of their $900 tickets.

"There are a limited number of temporary seating areas inside the stadium that have not been fully completed," the NFL said in a statement issued two hours before the 5:30 p.m. CST kickoff.

"We are working to resolve the matter and expect that by game time most of the fans affected will have been accommodated in their seats or relocated to similar or better seats."

Long lineups at security checks, elevators and washrooms also had fans grumbling as an expected record crowd of over 100,000 filled the state-of-art $1.2 billion stadium.

After a week of miserable weather, Mother Nature finally cooperated and allowed workers time to remove snow from the roof of Cowboys Stadium after massive chucks of ice slid off the biggest domed stadium in the United States Friday injuring several people.

Packers and Steelers fans along with dozens of celebrities made their way to the stadium early Sunday and playfully taunted each other with hours to go until kickoff.

Tight security was in place around the sprawling facility.

(Editing by Frank Pingue)