The 26-year-old defender moved from the Blades to Sir Bobby Robson's side two years ago but has found it difficult to break into the first team at St James' Park.
Warnock had been keen to bring a left-back to the club in readiness for the two legs of the Worthington Cup semi-final against Liverpool after Jon Harley's loan spell at Bramall Lane ended earlier this week.
"Wayne had the choice of two or three clubs to join but jumped at the chance of coming back here when he heard of our interest," Warnock told the club's official website.
"There is no chance of making the deal permanent but a month's loan will help us out enormously and suits Wayne, who will now play in four televised games in succession with us."