Steven Fletcher snatched his eighth Premier League goal of the season to hand Sunderland a 1-0 win over Southampton at a saturated St Mary's.
The Scotland striker settled the match in Martin O'Neill's side's favour when he swept the ball into the net from eight yards out on 42 minutes after a mishit Stephane Sessegnon effort had fallen kindly to him from Adam Johnson's cross.
Southampton tried to engineer a route back into a contest spoiled somewhat by some wretched weather conditions, but could not find a way to cut through a visiting defence superbly organised by John O'Shea and Carlos Cuellar.
Sunderland - who had lost three of their four matches in December - collect a second Premier League away win of the season, while Southampton lost their first Premier League home match since October 28.
The Black Cats move up to 15th place in the standings with 19 points from 18 matches, while 17-placed Southampton have 15 from their 17 outings ahead of Wigan Athletic on goal difference.
The visiting side made a bright start to the afternoon as Sessegnon saw an effort superbly nudged over the bar from distance by home goalkeeper Kelvin Davis on two minutes.
The disappointing Jason Puncheon wasted an obvious opening for the home side two minutes later when the ball broke to him from a Rickie Lambert pass, but he screwed the shot wide of goal when he had time to take a touch rather than rush himself.
Lambert saw a low free-kick deflect wide off the boot of Craig Gardner as Southampton continued to push and probe. At least in the opening moments of the match.
Gaston Ramirez also displayed his skills with a free-kick from 22 yards halted by Simon Mignolet after Fletcher had flicked a Gardner cross wide seconds earlier when he should have gone with his head rather than feet.
Cuellar showed his class with a fine tackle to halt the progress of Lambert as he threatened to bound clear before Sunderland found their range to bury what proved to be the winning goal coming from the reactions of Fletcher.
The second half went according to plan for Sunderland as they managed to frustrate Southampton almost into submission with their ongoing unwillingness to concede delighting the large posse of travelling supporters.
A Gardner cross almost found Fletcher sliding in to convert early in the second half, but Sunderland were content to soak it up and counter attack in more ways than one on such a sodden day.
Southampton managed little of note with Jose Fonte managing to head wide of goal from substitute Steve de Ridder's corner midway through the half. It sailed wide via the head of Jack Colback, but was already missing the rigging.
Another substitute in the shape of Guilherme Do Prado saw an effort deflect wide deep into injury time, but in keeping with the theme of the afternoon, the home fans were left dejected and wondering what might have been as their last home game of the year ended in defeat.
MAN OF THE MATCH
John O'Shea (Sunderland) - Proved a real class act at the back alongside Carlos Cuellar, which should give Sunderland fans plenty of optimism if the pair can maintain similar levels of concentration for the rest of the season.
Southampton: K. Davis 7, Clyne 5, Fonte 5, Yoshida 6, Shaw 6, Puncheon 5, Schneiderlin 5, Cork 5, Ramírez 6, Lambert 6, Mayuka 5. Subs: S. Davis 6, Do Prado 6, De Ridder 7
Sunderland: Mignolet 7, Gardner 7, Rose 7, O'Shea 8, Cuellar 8, Larsson 6, Colback 6, Johnson 7, McClean 6, Sessegnon 6, Fletcher 8. Subs: Bardsley 6, Campbell 6, Vaughan 6