Marc Sneyd hit a 50-metre penalty to bag the points for Hull in a low-quality game at St Helens.
The rain hammered down from the first minute to the last and it was the solo effort and game management of Sneyd that won it for the Challenge Cup finalists.
With the game on a knife-edge and the clock ticking down Hull took their opportunity to land a penalty from the halfway line, Saints turning down an easier opportunity minutes earlier which proved to be the difference between the sides.
The rain-soaked turf was the only obstacle Sneyd had to contend with and his effort was bang on target to give Lee Radford’s men the opportunity to close the game out.
It could have been a different story for Saints, who fluffed some golden opportunities in the first half.
However, it was Justin Holbrook’s side who registered the first points of the evening as Regan Grace touched down in style out wide after Mark Percival had created the opening.
Percival struck the conversion but Hull looked to get back into it straight away, with full-back Jake Connor going close.
The Percival-Grace connection should have yielded another try just before the half-hour mark but the rookie winger dropped the opportunity when it looked easier to score.
The sheets of rain were beginning to take their toll and handling errors from both sides were impacting the quality of the clash.
Hull finally understood the need to keep it tight and when they had some rare field position they began to make it pay. Liam Watts nearly barged over and Danny Houghton was beginning to cause problems from dummy half, and eventually they made it count through Sneyd five minutes from half-time.
The classy half-back’s footwork deceived the big Saints defenders and he stepped his way to the line before levelling it up with a routine conversion.
Saints spurned the chance to nudge themselves ahead seven minutes after the break through what would have been a simple penalty chance for Percival, as they instead ran the ball and ended up with nothing.
The entrance of scrum-half Matty Smith signalled some intent from Holbrook, who sensed the Airlie Birds were there for the taking, but it was beginning to become a tale of too many missed opportunities for the home side as the killer pass was consistently put to the floor.
The game was still in the balance with 20 minutes remaining with both teams cancelling each other out.
However, Sneyd and Hull pointed the way forward with a massive 50-metre penalty that sailed over the sticks to put FC’s nose in front.
Saints threw everything at the visitors in the closing stages with charges from James Roby, Zeb Taia and Alex Walmsley, but each and every time the Hull defence was up to the task and the win cements their place in the top three of Super League.