The 19,000-seat Saddledome is one of the feature buildings on the Calgary Stampede grounds.
"We have reports that — yes — it is up to the 10th row in the Saddledome and ... I think that really paints a very clear picture of what kinds of volumes of water we are dealing with," Trevor Daroux, the city's deputy police chief, said Friday.
Officials said there is little that can be done to pump out the building because there is too much water surrounding the building. And if levels have filled the lower areas under the seats, the Flames dressing room will be full.
The team did not respond to requests for comment. It used its Twitter account to keep employees away.
"Flames employees — do not attempt to go to the Saddledome today," the team tweeted.
The Stampede, the city's premier summer event and a major international tourist attraction, is scheduled to start July 5.
The rodeo grounds were a muddy lake Friday with water lapping at the roofs of the animal barns.
The mayor pledged the show will go on.
"All of those volunteers that make it happen every single year will make it work," Naheed Nenshi said at a news conference Friday.