The Russian Grand Prix's final practice session was cancelled on Saturday morning after torrential rain left the Sochi circuit under water.
Qualifying for Sunday's 15th round of the Formula One season was now "the priority," race director Michael Masi said.
"As we can see already this morning, the weather has gone up and down like a yoyo and the intensity of the rain has started increasing with some thunder already joining us," he added.
The third and final qualifying session had been scheduled for 11.00 local time (0800 GMT) with qualifying at 14.00.
"From what we've seen from the forecast we will have this level of rain to 1.30 to 2pm local time (10:30-11:00 GMT) and then decreasing. Priority... is Formula One qualifying."
A Formula 3 race scheduled for Saturday was run on Friday evening in anticipation of the bad weather. A Formula 2 sprint race, scheduled for Saturday, was postponed, with F1's official twitter account posting a video of lightning cracking above the rain-washed track and the caption "WHOA!".
"The determining factor this afternoon will be the light," Masi said.
"Sunset locally is about 18.15 but with weather conditions like this light diminishes far earlier. That will be our cut-off point. If qualifying isn't able to happen today we will hold qualifying, as has happened before, on Sunday morning."
Championship leader Max Verstappen tweeted: "So far, today brings lots of rain. Let's see how the day will go," with a photo of the Dutch driver holding a Red Bull umbrella.
- Max Verstappen (@Max33Verstappen) September 25, 2021
Typhoons delayed qualifying to Sunday at the Japan Grand Prix in 2004, 2010 and 2019.
This is the second time this season that rain has disrupted the championship.
A deluge at Spa-Francorchamps, Belgium, at the end of August, ended the race after just three minutes with Dutchman Max Verstappen (Red Bull) awarded the win ahead of Williams' George Russell and Lewis Hamilton.
In accordance with the rules, the drivers were awarded half points.
On a track where they have won every race since 2014, Mercedes dominated free practice on Friday, with Finn Valtteri Bottas ahead of seven-time champion Hamilton.
Red Bull's Max Verstappen has a five-point championship lead over Hamilton but the Dutchman will start at the back of the grid on Sunday after his team opted to put a new engine in his car.
Hamilton is aiming for his fifth success in Sochi to bring his career total to an unprecedented 100 wins.