It has already rained at Sepang on Sunday and even more wet weather is forecast for the late afternoon race start in Malaysia.
Fernando Alonso said the chance of race rain is "between 70 to 80 per cent", but others have put the likelihood at closer to a certainty.
"We know that here, when it rains, it falls in torrents," said the Spaniard, who admitted he is hoping for bad weather to boost his chances of a podium finish.
Lewis Hamilton agrees that the chance of a wet race is very high, and said it is surprising that the track sessions so far have not been rain-affected.
"I’m told a big cloud is on its way," said the McLaren driver.