For the Accies an unexpected run of three victories had hauled them out of the relegation zone while the Saints had enjoyed five games without conceding a goal.
But at the end of 90 minutes at New Douglas Park it was St Johnstone who were celebrating after a convincing victory.
The warning signs were there for the hosts as early as the sixth minute when David McEwan was forced to save Ross Forsyth's close-range effort.
However, 11 minutes later the normally reliable McEwan was the villain when he misjudged a speculative Forsyth ball from 35 yards leaving Chris Hay with the simple task of pushing the ball home.
Accies had their chances - mostly from set pieces - and Brian Carrigan was unlucky to see a shot cannon off the post following a neat flick from Pat Keogh.
Carrigan and Scott Tunbridge then wasted two free-kicks before Saints' Paul Sheerin showed them how it should be done, drilling the ball home from 20 yards on 39 minutes.
In the second half as the wind and rain swirled around the half-built stadium, the Saints gradually tightened their grip on the game.
And Ryan McCann duly wrapped up the points on 69 minutes after Peter MacDonald's ball across goal allowed him to tap in at the right-hand post from four yards.
Hamilton's night got worse when Tunbridge was carried off leaving the home side to finish the match with just ten men.
For St Johnstone however, the division's most improved side, it is now six games without conceding a goal and a happy New Year for manager John Connolly.