The on-loan Nottingham Forest striker demonstrated his blistering pace and lethal finishing to good effect which enabled the Imps to survive a second-half onslaught from the Saddlers.
Walsall's top of the table tenure is now under serious threat as they appear to have lost their way in recent games.
Following their recent slump in form and heavy criticism from some of their fans, Walsall disappointingly failed to lift themselves out of the doldrums.
Lincoln, with the second best goalscoring record in the Football League, ran up against the team claiming the best defensive record but it was the Imps who generally took the honours as they demonstrated why they are currently in such a challenging position for promotion.
In front of the Sky television cameras on a pitch which cut up easily following persistent rain during the day, Walsall made heavy weather of their task.
They struggled to cut out the threat of the skilful Lee Frecklington and found themselves chasing the game.
Skipper Michael Dobson, substituted at the break, had a nightmare game and Lincoln capitalised upon his mistakes to score twice through Weir-Daley in the first half.
Suddenly Walsall have lost their way and are struggling to find their early season form, while in sharp contrast Lincoln are closing the gap and look to be strong promotion candidates.
They are a fast moving side with Frecklington, aided by Scott Kerr, the driving force as he demonstrated by keeping Walsall's defence on the hop.
It was Frecklington who cleverly opened up the Saddlers defence to create the opening from which Weir-Daley opened the scoring after 15 minutes with a cross-shot which Clayton Ince could only finger-tip against the post and into the net.
To their credit Walsall's response was immediate with the equaliser coming in less than a minute when Dean Keates set up Hector Sam to score with an angled drive.
Sam was industrious and enjoyed a fine duel with Nat Brown who emerged as the Imps' top defender.
A frustrated Walsall attempted to dominate the game but a bad cross-field pass by Dobson led to Ryan Amoo collecting the ball to send the ever-dangerous Weir-Daley clear to notch his second goal of the match in the 42nd minute.
In the second half the Imps were subjected to some tremendous pressure from a Walsall side attempting to avoid only their second home defeat of the season.
Martin Butler continued to struggle with some weak shooting in front of goal when he wasted a couple of clear-cut openings with Lincoln in danger of collapsing.
Scott Dann was denied a 75th minute equaliser by a reflex save from Alan Marriott which generally summed up Walsall's frustrating second half.