After going through the regular season undefeated, the Raiders couldn't bounce back from last week's loss to Manly in a six tries to four defeat at Campbelltown Stadium.

"We just made far too many mistakes, and didn't handle the ball at the right time of the game," Raiders coach Dean Souter said.

"It was [disappointing], but that's part and parcel of coaching young blokes.

"You can bring them along as much as you can and the learning curve gets deeper, and that goes with the staff as well.

"You live and learn."

Canberra's under-20 clash with South Sydney at Erskineville Oval finished six minutes early due to hail and torrential rain.

Souths won the match 36-22, but Raiders coach Mick Mantelli said officials were left with no option but to call an early halt, with hail "in between marble and golf ball size" pelting the ground.

"I've never seen a game called off for weather," Mantelli said.

"There was six minutes to go, but the NRL made the decision."

The loss means the Raiders dropped to eighth on the ladder after winning their previous two games against the Tigers and Storm.

Mantelli expects key playmaker Lachlan Croker to return from his shoulder injury after next week's representative break.

Meanwhile, Mounties' seven-game winning streak in the NSW Cup came to an end with a 16-10 loss to Penrith in the top-of-the-table clash.