The second free practice session for the United States Grand Prix has been cancelled due to safety risks brought on by stormy weather.

With heavy rain predicted this weekend due to a storm front being pushed towards Texas by Hurricane Patricia south of Mexico, though FP1 took place in damp conditions, rain intensified just as FP2 was due to get away.

Furthermore, with lightning being reported in the surrounding area, stewards initially determined it to be too dangerous for marshals to work on track, therefore delaying the start, while spectators were also urged to seek shelter.

However, with rain falling harder and visibility reduced - and more extreme weather potentially on the way -, with no medical helicopter able to operate for at least two hours, the decision was taken to cancel the session altogether.

Bad weather is expected to continue into Saturday, raising fears FP3 and qualifying could be affected, while latest forecasts suggest it could extend to Sunday as well.