Heavy security and sun greet fans for American football's Super Bowl 50

A Santa Clara police officer on duty before the start of American football's Super Bowl 50 in California on Sunday.
A Santa Clara police officer on duty before the start of American football's Super Bowl 50 in California on Sunday.PHOTO: EPA
Police and military security patrolling several hours before the start of the NFL's Super Bowl 50 on Feb 7, 2016.
Police and military security patrolling several hours before the start of the NFL's Super Bowl 50 on Feb 7, 2016. PHOTO: EPA
A fan going through security prior to Super Bowl 50 at Levi's Stadium on Feb 7, 2016.
A fan going through security prior to Super Bowl 50 at Levi's Stadium on Feb 7, 2016. PHOTO: AFP
Fans of the Denver Broncos entering the stadium prior to Super Bowl 50 at Levi's Stadium on Feb 7, 2016.
Fans of the Denver Broncos entering the stadium prior to Super Bowl 50 at Levi's Stadium on Feb 7, 2016. PHOTO: AFP
Fans entering the stadium prior to Super Bowl 50 at Levi's Stadium on Feb 7, 2016.
Fans entering the stadium prior to Super Bowl 50 at Levi's Stadium on Feb 7, 2016.PHOTO: AFP
Fans entering the stadium prior to Super Bowl 50 at Levi's Stadium on Feb 7, 2016.
Fans entering the stadium prior to Super Bowl 50 at Levi's Stadium on Feb 7, 2016. PHOTO: AFP

SANTA CLARA, California (REUTERS) - Heavy security and brilliant sunshine greeted football fans as they descended on Levi's Stadium for Super Bowl 50 between the Denver Broncos and Carolina Panthers on Sunday.

As if it had been specially ordered by the National Football League for the Golden anniversary, Mother Nature delivered perfect party weather with blue skies and unseasonably warm temperatures hovering around 21 degrees Celsius.

The weather helped lighten the mood as thousands of fans passed through heavy security put in place following recent attacks in San Bernardino, Calif and Paris.

Earlier in the week, US Secretary of Homeland Security Jeh Johnson said law enforcement officials had worked with their French counterparts to learn from last year's deadly attacks in the French capital.

Those attacks included the detonation of a suicide vest outside a soccer match.

Heavily armed soldiers backed up by armoured vehicles ringed an imposing security perimeter around the state-of-the-art stadium in Silicon Valley.

"It looks like Operation Desert Storm," Matt Ciszkawski, 44, of the Bay Area said with a laugh.

Inside the security ring, bomb-sniffing dogs and law enforcement officers patrolled the complex while fans entering the stadium faced airport style security, passing through metal detectors and pat downs.

Overhead Black Hawk helicopters circled while Air Force fighter jets enforced a no fly zone.

Fans looking for last minute deals for tickets were not going to find them with the average price on resale site StubHub sitting at US$4,577 just hours before the opening kickoff, and at least one ticket selling for US$27,000.

Buyers from as far away as England, Germany, Kuwait and even New Zealand have purchased tickets for Super Bowl 50.

While the 17-1 Panthers entered the championship game as almost a touchdown favourite the majority of the 72,000 fans filing into Levi's Stadium were decked out in Broncos orange.

One of the big questions hanging over the Super Bowl is whether it will be Denver quarterback Peyton Manning's last game of an illustrious career that has included a record five league most valuable player awards.

As Manning stepped onto the field for warmups fans reached for their cameras to record what could be the future Hall of Famer's last NFL appearance.

ESPN reported that Manning was near tears when he addressed the team on Saturday but gave no hint to team mates as to whether this was his last game.