Since the knockout qualifying system was introduced to Formula 1® at the start of 2006, there has been only one occasion that Q3 has been completely cancelled. It happened at COTA, on the 2015 United States Grand Prix weekend. Heavy rain and flood warnings had already led to limited running in practice, with the Friday afternoon session cancelled due to the treacherous conditions.
Final practice on Saturday morning took place without fans in the grandstands due to safety concerns. Few laps were run as heavy rain continued to fall. After a three-hour rain delay, the decision was taken to delay qualifying until Sunday morning. But even then, the rain continued.
A red flag delayed proceedings in Sunday’s Q1 session and with further downfalls approaching, getting a good lap time in Q2 became imperative. The session would prove to set the grid for the Grand Prix, with Q3 cancelled as the rain worsened. It is the only time that lap times from Q2 have set the grid. The Grand Prix took place later that day on a drying track.