The towering centre-back left the Magpies for Weymouth last summer but the recent form of Sam Poole and his brother Michael Walker have kept him out of the side.
Nathan Walker will be a valuable addition to Phil Simkin’s men, who desperately need to strengthen their defence after shipping 22 goals in their last seven league games.
Weymouth player-boss Jason Matthews told Echosport: “Nathan has gone back to Dorchester on a month’s loan.
“He needs to get games and has been frustrated with the lack of opportunities here.
“Both Sam and Michael have done well of late and, as a result, Nathan has been kept out of the side.
“He has asked to go out on loan and we have given him that opportunity.”
Nathan Walker played a major part in Dorchester’s run to the second round of the FA Cup last season, but things are very different now with the county town outfit fighting for survival in Skrill South.
The Magpies currently sit seven points adrift of safety at the foot of the table and are likely to be hard pushed to get anything at Chelmsford City tomorrow (3pm).
The Clarets may only lie 13th at present but they have only lost one of their last nine in all competitions.
Dorchester manager Simkin added: “I am delighted to have Nathan back on board because he has been a big player for us in the past, and will no doubt make a big difference for lots of reasons.
“As well as his defensive qualities, he will get the dressing room going a bit and is also capable of nicking a goal or two from set pieces.
“He is someone I have worked with for years and exactly the type of player we need at the moment.”
Commenting on the Clarets, he went on to say: “A new manager has gone in up there, and there has been a bit of an injection of cash too, with new players coming in.
“As a result, they have been going well recently and are a completely different proposition to the side we beat earlier in the season.
“It’s going to be tough but we need to get on some sort of run soon because the gap is beginning to widen.
“Hopefully we can get something tomorrow and kick on from there.”
Steve Walker and Clive Makoni will again miss out for the Magpies this weekend through suspension.
Magpies (from): Walker-Harris, Case, Colmer, Jermyn, N Walker, Smeeton, Lanahan, Crittenden, Gleeson, Losasso, Byerley, Twyford, Munday, Way, Tennant, Godfrey, Brooks.