MotoGP has been forced to cancel all of Saturday's remaining practice sessions at Austin due to the threat of lightning in the area.
Promoter Dorna announced earlier on Saturday that all free practice sessions would be reduced to a 20-minute duration, starting with third Moto3 practice that was due to start at 5pm UK time (11am local time).
But moments before that session was due to start, an order was given for fans to clear grandstands and seek shelter due to "a dangerous storm with lightning in the area".
MotoGP added that its qualifying schedule was also "subject to weather conditions", but has since confirmed Moto3 qualifying will take place at 6.35pm UK time.
Heavy rain has now returned to the circuit, and more is forecast to arrive in a couple of hours' time when qualifying is due to take place.