Heavy rain postpones Sao Paulo Grand Prix qualifying until Sunday
After being delayed for two hours with no improvement in conditions, amid fading daylight, officials decided the hour-long session could not proceed and moved it to the morning of the race.
"It's a pity but the conditions are not safe to drive, as simple as that," Formula One chief executive Stefano Domenicali told F1 television in a pitlane interview as the rain continued to fall. "Racing in these conditions is impossible."
The governing FIA said in a statement that the decision was taken due to poor visibility and standing water.
"The safety of drivers, team members, volunteers, officials and spectators is our main priority," it said. "A decision on a start time for qualifying tomorrow morning will be taken as soon as possible."
Qualifying has been held on a Sunday in the past, most recently at the 2019 Japanese Grand Prix when a passing typhoon forced a delay.
Saturday's sprint race, won by Lando Norris in a McLaren one-two, was held in dry conditions as was Friday practice and sprint qualifying.
More rain is forecast for Sunday.
Brazil is the 21st round of the 24-race championship and the last of an American treble on successive weekends.
Red Bull's triple world champion Max Verstappen leads closest rival Norris by 44 points and any race cancellation would have a huge impact on the title outcome.
If all goes ahead as planned, Verstappen will have a five place grid penalty for the race after exceeding his engine allocation.