The Formula 1 United States Grand Prix faces uncertainty as heavy storms lashed the city here, a result of Hurricane Patricia.
The second practice at the Circuit of the Americas (COTA) was called off as a result of the hurricane. With up to 30 cm of rain forecast to fall on Saturday, qualifying could be postponed until Sunday.
"If it's like this, we can't run. It does not look good," Ferrari driver Sebastian Vettel was quoted as saying by BBC.
In the first practice, which was affected by heavy showers, Mercedes driver Nico Rosberg was the quickest.
Officials have not yet made specific contingency plans as the weather is changing very rapidly. But the sport's governing body FIA says it will try changing the schedule so that qualifying can take place if there is any sign of dry weather.
The rough weather is supposed to end by Sunday - the day when the race is scheduled. Officials have reportedly even thought of staging the qualifying on Sunday, just before the race, if possible. Otherwise the grid will be decided by some other method.
The storm is even raising concerns about the forthcoming race in Mexico next weekend. If it happens to cause damage to Mexico City, it could be difficult to have the race on the Autodromo Hermanos Rodriguez track, which is hosting a Grand Prix for the first time since 1992.