The intense heat at Hillsborough was always going to influence this League One contest and so it proved as substitute Tyreeq Bakinson climbed from the bench to give the Owls a 1-0 win over Charlton.
Bakinson was one of three substitutes introduced on the hour and the move paid dividends as the new recruit netted his maiden goal in Wednesday colours.
The Londoners had the best of the few chances created overall and may well feel the defeat was undeserved.
But the Owls kept plugging away and had enough in the tank to motor on and claim victory.
In blazing S6 conditions, the first half was incident-free until the half-hour mark when Scott Fraser spooned a good opportunity high over the bar.
Steven Sessegnon, a tricky operator down the left channel, smashed a low shot narrowly wide moments later as the Addicks looked to profit from long spells of possession.
And they should have done exactly that six minutes before the break. A defensive mix-up saw the ball fall perfectly for Corey Blackett-Taylor 10 yards out and with David Stockdale stranded, the goal was at the wideman’s mercy.
But just as Charlton were all but celebrating, Liam Palmer raced back to hoof off the line and the Owls breathed a sigh of relief.
The second half needed a spark and Callum Paterson was a whisker away from providing it straight after the restart.
Josh Windass broke down the right, crossed low, and the onrushing Paterson needed an extra inch to convert.
Charlton hit back when the dangerous Blackett-Taylor twice carved openings, the first of which fell wide and the second into the arms of Stockdale.
Darren Moore then made that triple change and Wednesday, attacking the Kop, started to find some real rhythm.
And 10 minutes from time came the reward and the points. Windass delivered a super cross right into the danger zone and Bakinson rose to power an unstoppable header high into the net.
Sylla Sow and Windass had sights of goal late on to make the game safe, but Bakinson’s strike proved enough to send Wednesday towards the summit of the table.
Wednesday: Stockdale, Hunt (James 72), Ihiekwe, Heneghan, Palmer, Vaulks (Byers 58), Bannan (Sow 80) Dele-Bashiru, (Bakinson 58), Johnson, Paterson (Gregory 58), Windass