The 22-year-old has made 47 appearances for Wigan since making his debut in 2012.
“Logan needs regular Super League rugby at this stage of his career. Not knowing where he is playing every week has been frustrating for Logan and we made a difficult decision to put his personal position ahead of the team,” said Wigan director of rugby Kris Radlinski, according to his club’s official website.
“Salford gain a totally committed professional who will work harder than anybody to help the team.”
Tomkins previously played for Salford 2014 on loan. He is pleased to be heading back there.
“I’m really grateful to Shaun Wane and Kris for allowing me this opportunity to join Salford until the end of the season,” he said.
“We are all in agreement that playing as much at Super League level is what I need right now and I’m looking forward to continuing my development as a player.”