Pakistan, Oct. 3 -- Formula 1's governing body has declared this weekend's Singapore Grand Prix a 'heat hazard' race.

The FIA's ruling, triggered because temperatures are predicted to exceed 31C amid high humidity in the tropical environment, means drivers could be using cooling vests during the race.

Using the vests is not mandatory but teams must fit the system to their cars to ensure any drivers not using them does not gain an advantage by having a lighter car.

The Singapore Grand Prix marks the first time a race has been designated as a heat hazard under a new rule that was introduced this year.

However, it will not be the first time drivers have used the vests - teams have been testing them intermittently through the year.

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