The second practice session for the Chinese Grand Prix was scrapped due to low-lying cloud impacting visibility, leaving officials with no choice but to abandon proceedings on safety grounds.
Damp and misty conditions meant that while the track was fine for drivers, the medical helicopter would have been unable to land at the designated hospital, if such a situation was required.
Race Control evaluated the situation every 10 minutes, before eventually declaring that the session would not start, 15 minutes before the end of the planned running.
"[The helicopter] can’t land at the hospital which is 38km away unfortunately," said Race Director Charlie Whiting.
"It looks reasonable here, there are helicopters flying, but they can’t land at the airport which is in downtown Shanghai."
Max Verstappen had set the quickest time during the first session, which was also interrupted due to the same weather issues.