AUSTIN, Texas (Reuters) -Formula One's governing body declared a heat hazard for the second race in a row at the U.S. Grand Prix in Austin on Thursday.
Race director Rui Marques said in a statement sent to teams that an official forecast predicted the heat index would be more than 31 degrees Celsius (87.8°F) at some time during the Saturday sprint or Sunday Grand Prix.
The regulation was invoked for the first time at this month's Singapore Grand Prix due to the temperatures and high humidity.
The regulation was brought in after drivers suffered exhaustion in the 2023 Qatar Grand Prix and means drivers can either wear a cooling vest, which circulates cold liquid through tubes to maintain body temperature, or add extra ballast to their cars.
The vests are set to become mandatory in hot conditions from next season but are not universally popular, with some drivers preferring not to use them.
"I haven't used the vest. I'm also not intending to use it because I feel like this needs to be a driver choice," Red Bull's four-times world champion Max Verstappen said in Singapore.
(Reporting by Alan Baldwin, editing by Toby Davis)
