A barrage of wind, rain and hail took its toll at Rodney Parade, with referee Andrew Small forced to take the players off the pitch five minutes before the break.
They returned after a short interlude and Saints went on to secure a five-try success that takes them a step closer to earning a home semi-final.
But the extreme weather was the main talking point after the game, with Mallinder amazed by what he had witnessed.
“I’ve played and been involved in some snow storms, some hail storms but never as severe as that,” said the former Sale full-back.
“To see players in open play turning round and not looking at the ball was incredible. The referee did the right thing to get off for a few minutes and then continue.
“It was difficult. We’d said before the game that it wasn’t a bad day. We’d talked about it being bad conditions but when we first came out it was just a little bit of wind, a bit wet under foot but generally fine.
“It wasn’t until the hail and the rain came down and the lads were actually in the changing rooms shivering.
“It all makes me even more proud of the players and the way they played.”