Pep Guardiola and his squad hit the city to celebrate their securing four titles in a row with a 3-1 win over West Ham earlier this month.
It was slightly bittersweet following their 2-1 FA Cup Final defeat to arch-rivals Manchester United on Saturday.
But the loss proved no dampener for the players, including striker Erling Haaland, who sprayed champagne over the massed ranks of adoring fans.
The rain left many in the city soggy but it was nothing compared with some areas where more than an inch fell in the afternoon.
The Met Office issued a yellow weather warning from midday until 8pm for the North and South West, with flooding, power cuts, and travel delays forecast.
Holidaymakers hoping for a late May coastal getaway faced long hold-ups in Devon when the A38 was closed in both directions due to a fatal smash.
The M6 southbound was down to one lane following an accident, while a snarled M23 southbound delayed many heading to Gatwick.
Travellers taking ferries to France from the Port of Dover faced two-hour queues due to the weight of traffic.
The rain did stay away from Wembley, where Oscar-winner Dustin Hoffman, 86, was among those watching Southampton win the Championship play-off.
More than 20 million leisure journeys were made by car over the weekend — the most since pre-pandemic levels in 2019, according to the RAC.
Travel chaos is expected to continue today as 3.4million hit the roads once more.
Many will face more rain, with scattered showers predicted for most areas.
But sunny spells will return from Wednesday, with 18C highs.