Powell, currently housed in the Monroe Correctional Complex, was convicted in June 2012 of 14 counts of voyeurism for taking surreptitious photographs of two girls in his Puyallup neighborhood. He was sentenced to up to 30 months in prison.
Washington officials said they have notified Powell's victims and local law enforcement about his scheduled release.
Law enforcement found the photos of the neighborhood children during a search of Powell's home for evidence about his missing daughter-in-law. Susan Cox Powell, 28, disappeared from her home in West Valley City in December 2009.
Josh Powell, her husband and Steve's son, moved to Puyallup with their two sons shortly afterward; they lived with Steve Powell. Josh Powell was the only "person of interest" in his wife's disappearance. West Valley City Police closed their investigation in May.
Steve Powell, however, admitted to law officers and media that he was in love with his daughter-in-law, penning songs for her and secretly taking photographs of her including some of Susan in a partial state of undress.
Chuck Cox, Susan's father, said Thursday that Powell's release was out of his control.
"That's between the state and Steve," he said. "We're still looking for our daughter."
Since Powell went to prison, one tragedy after another has beset his family. Josh Powell, 36, killed himself and his sons Charlie, 7, and Braden, 5, in February 2012, in a deliberately set fire that erupted moments after the boys arrived at the rental home for a supervised visit. Michael Powell, another son of Steve Powell, committed suicide in February 2013 by jumping off a parking structure near his apartment in Minneapolis, where he was a graduate student at the University of Minnesota.
Powell had been eligible for an early release in May, but Washington authorities revoked that date because of concern about his release plan, which spelled out such things as living arrangements, work opportunities, etc.