RadioTimes.com brings you up to speed ahead of Formula 1's first ever 'heat hazard' race. What is a 'heat hazard' race in Formula 1? A 'heat hazard' can be declared if pre-race weekend forecasts suggest temperatures will hit 31°c during a Sprint or Grand Prix. However, drivers are not mandated to wear the actual cooling vests, which comprise a series of tubes flowing with cooling fluids. Numerous drivers reported medical issues during and after the race, including Esteban Ocon, who told reporters he was sick inside his race helmet during the Grand Prix.