The Hampshire batsman has joined for the final two County Championship group games and for one match in the T20 Blast.
He will make his debut in the Championship fixture against Northamptonshire at Wantage Road tomorrow.
The 31-year-old right-hander, formerly with Kent, will also play in the Championship Roses game at Emerald Headingley the following week and against Nottinghamshire at Trent Bridge this coming Friday in the T20 Blast.
Northeast is the second loan signing made by Yorkshire in the space of eight days after the recruitment of Surrey opener Mark Stoneman for five of the last six T20 group games.
Stoneman is unavailable for the Nottinghamshire T20 as Surrey want him to focus on their own double-header of Championship action that punctuates the closing stages of the T20 group phase.
Yorkshire have acted in both instances due to the absence of seven players to England/injury, which has left them short in the batting department particularly.
Martyn Moxon, the Yorkshire director of cricket, is hopeful that Northeast will help the club to secure a top-two finish in County Championship Group Three, which would send them into the newly-created First Division when the tournament resumes late next month, thus giving them a crack at winning the trophy.
“We are thrilled to be able to cover the players currently with England or injured with a batsman of Sam’s quality,” said Moxon.
“Given the strength of our group, and with the last two rounds of County Championship fixtures determining the top two places, Sam will give us valuable experience and batting depth.
“Sam will also be available for the Vitality Blast match against Notts Outlaws when Mark Stoneman returns to Surrey.
“We are looking forward to welcoming Sam and working with him over the coming weeks.”
Prior to the three-and-a-half week break for T20, Yorkshire had climbed to second in Group Three, four points behind Lancashire after eight rounds of the 10-match group stage.
They face a Northamptonshire side who themselves have aspirations of reaching the top flight, lying third in the group, 12 points behind Yorkshire.
The importance of the match thus speaks for itself – as does the fact that Yorkshire would like to get on the right side of it, just as they did, but only just, when Northamptonshire visited Headingley earlier in the season.
Yorkshire won that game by one run – only the second time that they have won a Championship match by that margin, the other against Middlesex at Bradford in 1976.
It had the feel of a pivotal win for Steve Patterson and his men, who are hoping not merely to qualify for the First Division, but also to finish top of the group.
All that can be said is that the situation is in their own hands; Lancashire host winless Kent in Manchester next week before the Roses rivals meet in a potentially mouthwatering denouement on Yorkshire’s home patch.
Yorkshire’s challenge going into these last two group games is essentially the same that they have faced all season.
Namely, that of trying to score consistently sizeable first innings totals, something which, it is fair to say, despite their lofty league position, they have managed with only moderate success.
Prior to scoring 558 in their last Championship game against Sussex at Headingley, their highest total for over five years, Yorkshire had the fewest number of batting points of any team in the country.
They had been bowled out for under 200 (the minimum figure needed to achieve the first of five batting points on offer in each game) three times in their previous seven matches and had only twice passed 230 in their first innings.
The Sussex display, then, was a positive step forward and something to build on as Yorkshire attempt to take pressure off their bowling attack.
At the same time, the search for consistency is a work in progress, with one of the players that Yorkshire are missing, Dawid Malan, having scored 199 of those 558 runs against Sussex off his own bat.
Northeast’s recruitment should help the objective.
On the face of it, it is a curious move in that Northeast has been ever-present for Hampshire this season, scoring 358 runs in 13 innings at an average of 32.54, including 67 and 19 not out in their last Championship game against Somerset at Taunton.
However, it is understood that he is going to be leaving Hampshire altogether, with Hampshire last night signing the Middlesex batsman Nick Gubbins on loan ahead of a permanent deal.
Northeast’s services remains highly prized, with a career record of 10,723 first-class runs at 38.57 testament to his talent.
Some consider him to be one of the best batsmen never to have been capped, and he is not likely to be short of suitors looking ahead.
Whether Yorkshire will be interested on a permanent basis remains to be seen, but, for now, he is providing important cover at a time when the club are missing so many key players when there is so much at stake.