The 19-year-old England youth international joins Boro team-mate John Johnson at Sixfields as cover for number one Chris Dunn.
Dunn is out for around a month as he recovers from knee surgery and Steele will compete with fellow youngster Billy Lumley for a starting role.
Sampson said: "With the injury to Chris Dunn I feel we need another keeper on our books for the next few weeks.
"Jason has a good pedigree and is obviously well known and highly rated by Malcolm Crosby.
"We hope he can help us out and gain some valuable experience at the same time."
Source: Team Talk
Source: Team Talk