A freak hail storm and a poor refereeing decision threatened to halt St George Illawarra's winning run, but the Red V powered through the adversity to score a remarkable victory over Roosters in an Anzac Day clash that had it all at Allianz Stadium.

For the first time in six years, officials decided to pause the game when hail and lightning smashed the venue midway through the first half on Saturday.

Referee Gerard Sutton made the final decision to put the game into recess in the interest of player safety.

The game was stopped for about 40 minutes and 35,110 spectators rushed to find cover, but everyone was determined not to let the weather bring an end to the annual Anzac blockbuster.

"I think they made the right decision in the end, especially for the crowd and TV I suppose, and for the players on the field," Dragons skipper Ben Creagh said in the post-game press conference.

The last known game that had to be paused was Newcastle versus Broncos in 2009, which was also Darren Lockyer's 300th game, which was stopped due to lightning.

Officials decided to take a 40-minute half time break before resuming play on that occasion.

The Dragons had held a 10-0 advantage before the game was paused, thanks to a Peter Mata'utia try in the 18th minute and some Mitch Rein craftiness to sneak over from dummy half just as the rain started falling.

The Roosters came out firing after the unexpected break and Shaun Kenny-Dowall pounced on a loose ball in-goal when Josh Dugan fumbled a Mitchell Pearce kick in the 37th minute.

James Maloney nailed the conversion to take the score to 10-6.

Shortly after half time a bad call by the referee not to send a possible try upstairs sent Dragons players and supporters into furious disbelief.

Dylan Farrell was robbed of a try when he appeared to get a hand on the ball in-goal, only for the referee to judge the Dragons player had knocked the ball dead and refused to ask the video ref.

Replays on the big screen clearly showed Farrell had grounded the ball and it should have been awarded, but by the time the referee realised his mistake it was too late.

Dragons coach Paul McGregor wasn't sure how much he was allowed to say to media about the incident.

"I'm not allowed to comment am I?" McGregor asked.

"I can't comment on the referee.

"But we went to a decision on a dropout, a (Joel) Thompson offside, then we didn't go to the box for a try.

"It's disappointing but that's the way it is."

Creagh was also baffled by the referee's decision not to review the play, especially after the insistence of Farrell and Jason Nightingale in particular.

"They wanted to look at the video and it was a shame he didn't because we got up the other end of the field and (saw) it was a try,"  Creagh said.

"There's a lot of 50-50 calls but in that case, especially how slow and wet the ground was the ball held up there, it would have been good for the ref to go upstairs and at least have a look.

"It was a big game, a big play, but that's footy."

Luckily, Roosters forwards Dylan Napa and then Sio Siua Taukeaho gave away penalties later in the piece and Widdop slotted both conversions to extend the lead to 14-6.

Napa was reported for his high shot on Euan Aitken.

It was Napa's second report for the game, following a crusher tackle on Josh Dugan in the first half.

Daniel Tupou gave Roosters fans a glimpse of hope when he darted across to score off the back of a quick tap in the 71st minute to bring the margin to just two points.