This weekend’s Bahrain Grand Prix in Malaysia has been declared a heat-hazard race, the third time the designation has been used this year.

A heat hazard is an official status for an event where it is forecast that temperatures will be more than 31C at some point during the race.

The Sepang track, near Malaysia’s capital Kuala Lumpur, is close to the equator and has long been known as one of the most demanding for drivers.

Temperatures are forecast to be in the 31-33C region across the race weekend, with a high humidity level and chance of rain every day.

This weekend’s event is being held in Malaysia as a way of running the Bahrain race, which was postponed from its original April date because of the war in the Middle East.

A number of Bahrain-related activities are being planned across the weekend to emphasise the Gulf kingdom’s role in the event.

The heat-hazard ruling means drivers can use an in-car system that flows cooled liquid, such as glycol, through a system of pipes in a fireproof top worn under their overalls.

The cooling kit is not mandatory, but any driver who chooses not to use it has to carry 5kg of ballast in their car to ensure there is no competitive advantage.

Bahrain/Malaysia follows the Austrian and Italian Grands Prix in being declared a heat hazard this year.

The designation was first introduced last year, once the technology for the cooling vest had been developed.

Some drivers prefer not to use the cooling kit because of discomfort, and because there have been issues with the coolant running out before a grand prix is finished.

In that case, the liquid ends up at car temperature, which is considerably higher than ambient.

Temperatures in the cockpit of an F1 car can be more than 40C, and drivers are wearing several layers of fireproof clothing – in addition to a balaclava and helmet – so overheating is a serious concern.