The opening, on the eastward carriageway of the Mancunian Way, is 40ft (12m) profound and no less than 30ft (9m) wide.
Both carriageways have been fenced off between the Macdonald Inn, close Piccadilly Station, and Fairfield Road.
It is trusted an expansive water channel underneath the street dissolved, bringing about the street surface to collapse.
Around two weeks of downpour fell in around six hours in the city on Friday.
Geography master Dr Nigel Cassidy, of Keele College, said: "There is delicate dregs in there [under the road] and when it gets wet, as we had with this precipitation, the residue gets weaker.
"It can wash away sand and you wind up with a little pit opening up, especially if there is a broken sewer," he included.
Manchester City Chamber said the street could stay shut throughout the weekend "contingent upon the degree of the issue".
Enormous match delays
The conclusion is liable to include to more noteworthy clogging Sunday when Manchester City play Chelsea at the Etihad Stadium. The Mancunian Way is one of the fundamental courses to the ground from the west.
Witnesses said the opening had expanded in size and a piece of the asphalt has now disintegrated.
Board and United Utilities officers are at present surveying the scene.
Any stretched out street conclusion is liable to bring about additional blockage the city. There are broad roadworks close to its primary mentor station and additionally a conclusion on Oxford Street close to the college.
The street may stay shut for a few days, a committee representative said. Activity is being redirected.