First-five Areta Lama tried a drop goal, which struck the upright while winger Samu Kubunavanua spilled a pass at the tryline.
North Otago then turned it around with a dash of good fortune when English first-five Ben Palmer skied a penalty kick to the sideline, but schoolboy winger Matthew Vocea chased through and snatched what amounted to an attacking bomb.
Wanganui would turn the ball back over but lose it again, and Palmer would drift into a half gap, where lock Sonny Woodmass was partially blocked by inside runners, diving over for the converted try.
Needing at least a 12-point buffer from that wind as penalty kicks and long clearances would be difficult in the second half, Wanganui appeared to be looking down the barrel.
Yet fortune also smiled their way after halfback Lindsay Horrocks was fumbling some ruck ball, yet found centre Tevita Taufui, who broke through and chipped ahead.
Taufui and winger Simon Dibben swarmed on the North Otago fullback and turned the ball back over, where Horrocks took the last pick and go for 7-7.
It was a glimmer of hope given Wanganui had made a meal of their early weight of possession, with No8 Lasa Ulukuta's hands letting him down, while an option to spin wide from a corner lineout instead of the signature forwards maul was baffling.
Wanganui have always known how to play tight into the breeze and started the second half as they meant to go on with captain Peter Rowe, reserve Bryn Hudson, and Woodmass making some powerful runs, before North Otago's big men would smash them to ground.
Four key turnovers for trapped ball or holding on, in sight of the home team's line, left the observer to think it just would not be Wanganui's day.
North Otago captain Josh Clark and the rest of their pack were up for it.
A key change came when Palmer was replaced with Fenemor, who had the advantage of a long kicking game, but suddenly the shallow clearances and dropped backline ball that had blighted North Otago at Cooks Gardens returned.
Wanganui prop Viki Tofa all but put Woodmass away, but the ball went to ground.
Hudson scooped up a loose ruck ball and dashed 40m on his injured knee to bring Wanganui down for yet another crack.
Lama dummied into space, and then Hudson, Tofa, and reserve hooker Roman Tutauha all had a go at the line, before Wanganui spread to perhaps the only chink in North Otago's armour - Sagote running at Vocea - and the import beat his man to dive over near the posts.
For the next agonising 10 minutes, Wanganui forced turnovers but either through ineffective kicks or infringement could not get out of the danger zone, as North Otago's midfield brother combination - Tenina and Ekeroma Saulieoge - threatened to punch through.
The gap opened up on a kick return as Ekeroma Saulieoge beat reserve centre Jaye Flaws and fed Vocea, who redeemed himself by scoring in the corner.
It brought the spotlight onto Fenemor, but he could not convert and Wanganui defended desperately, forcing a turnover before clearing.
North Otago got a last penalty attempt, which Fenemor could not land.
Wanganui 14 (L Horrocks, R Sagote tries, A Malo 2 con) bt North Otago 12 (B Palmer, M Vocea tries, Palmer con) HT: 7-7.