City again did most of the hard work in the opening period, scoring three goals in the space of ten mesmerising minutes to blow Watford away for the second time in four matches away from home.
The Blues recorded a 5-0 win back in May that could have ended in double figures and despite a more resolute start by the Hornets on this occasion, the end result was actually worse as City hit another three after the break..
Raheem Sterling was recalled in place of Bernardo Silva for the only change from the side that thrashed Feyenoord in midweek.
With Sir Elton John and Noel Gallagher both sat watching in the Vicarage Road stands, it was City who quickly started to call the tune with the usual prods and probes around the opposition box.
As the Hertfordshire rain poured down, so the hosts seemed to drop deeper and deeper in defence, attempting to repel a flood of attacks and for 25 minutes or so, the plan worked well.
But City had not quite been able to find the final killer pass in the Hornets’ box and when Holebas’ free-kick was glanced wide by Richarlison, it served as a warning that a home goal could completely change the complexion of the game.
If it was a wake-up call, it was heeded and acted on almost immediately.
The Blues were awarded a free-kick midway in the Watford half and Kevin De Bruyne whipped in a trademark free-kick and Heurelho Gomes with 27 minutes played.
Four minutes later and Aguero had his second of the game to double City’s lead.
Gabriel Jesus did well to work his way past a couple of challenges and find David Silva and the skipper’s quick-thinking caught out the home defence and Gomes as his low cross found Aguero who tapped home from two yards out.
Watford looked shell-shocked and survived for another seven minutes before the Blues all-but wrapped up the points as Aguero found Jesus with a neat through ball and the Brazilian struck a low shot past Gomes.
That was 17 goals scored by the South American strike partnership in the last 10 games – not a bad return! And there was more to come.
Watford came out with more intent after the break and for a time, it seemed attack was the best form of attack as Ederson was finally called into action.
Then, just as happened in midweek against Feyenoord, it was the quiet before the storm as City went through the gears once more until the Hornets’ net was bulging again.
Silva, in plenty of space on the left, crossed in a beauty that Nicolas Otamendi headed firmly past Gomes to officially wrap up the points.
But the best goal was still to come with 81 minutes played as Aguero picked up the ball outside the Watford box, slalomed through three challenges before squeezing a low shot off the post and over the line to complete a memorable hat-trick and a miserable afternoon for the home side who must be sick of the sight of City.
There was time also, for a brief welcome cameo from Ilkay Gundogan, playing his first game since injuring his knee against the Hornets nine months ago.
With a minute of normal time left, Sterling skipped past a couple of challenges before being brought down in the box and the England winger stepped up to emphatically score the penalty himself on a chastening afternoon for the home side.
City, meanwhile, have scored 15 goals in the last three games and defences up and down the land will be quaking in their boots at the thought of facing this most potent of attacking forces.
De Bruyne’s free-kick and Aguero’s goal came at the perfect time, with Watford starting to finally look threatening at the other end.
City Matchday App star man: Sergio Aguero
A hat-trick and an assist – another superb afternoon’s work by the soon-to-be crowned greatest scorer in the Club’s history.
What it means:
City go top – and if Manchester United fail to win by more than four goals, the Blues will stay there going into next weekend.
City travel to The Hawthorns to take on West Bromwich Albion in the Carabao Cup third round on Wednesday before hosting rock-bottom Crystal Palace next Saturday in the Premier League.