Riley, 23, was the second highest try scorer in the competition last season, but has been forced out of the Wolves line-up since the arrival of Joel Monaghan.
Wolves boss Tony Smith said: “This move will give Chris the opportunity to play some regular first-team rugby. He is an experienced Super League player and at present we are unable to give him as much Super League game-time as we would like.
“This opportunity arose at Harlequins and Chris was happy to take it and play in the Super League on a more regular basis which will help prepare him for when he returns to us here at Warrington.”
Riley, who has scored 66 tries in 107 appearances after graduating from the club’s academy, will join team-mate Lee Mitchell in the capital, after it was confirmed his loan spell would be extended for a further month.