All the goals came in the second half, with leading marksman Sam Winnall bagging a brace after midfielder David Syers had opened the scoring.
But it needed two brilliant saves by Scunthorpe stopper Sam Slocombe to deny Rochdale before the visitors were reduced to 10 men in the 79th minute when full-back Michael Rose was sent off for a second bookable offence.
Kicking against the stormy elements, Scunthorpe were happy to reach the interval on level terms after Slocombe had reacted brilliantly to turn away a header from Rochdale's leading marksman Scott Hogan.
With the elements in their favour, in-form Iron took control in the second half.
Syers opened the scoring in the 57th minute, drilling a low 30-yard shot past goalkeeper Josh Lillis for his second goal in successive games.
Rochdale's hopes of a revival ended when Slocombe denied them again with a brilliant point-blank save to keep out a header from Graham Cummons.
Then, after Rose saw red for Dale, Winnall took centre stage with two goals in three minutes.
He made it 2-0 in the 82nd minute, crashing a right-footed shot into the top far corner.
Then, in the 84th minute, he broke free into the box to fire his 13th goal of the season past Lillis to take over as top marksman in League Two.