Lewis Hamilton says the tropical conditions at the Malaysian Grand Prix make it the toughest race of the year.
The Englishman, who won the first F1 race of the season in Australia last weekend, expects the humidity at Sepang to test all the drivers on Sunday.
"It was the hardest race I have ever competed in last season," said Hamilton. "You cannot begin to imagine how hot it gets in the car.
"The climate plays a major role in making it very tricky for all of us."
The race-time temperatures in Melbourne reached 39 degrees Celsius, higher than expected in Malaysia, but humidity at Sepang has been at more than 60%.
"They cannot have a much worse weekend than they had last weekend. I am sure they will recover and do a better job"
Hamilton, like most of the drivers, arrived as early as possible to acclimatise and says he will be well prepared for the heat.
"We've had a bit of a head start with the temperatures in Australia," the 23-year-old explained. "The focus is on making sure you are really well hydrated.
"Last year, I was drinking up to four litres a day in the build up to the race.
"It was one of the most physical events that I have ever come across, definitely.
"I think a lot of athletes would have struggled in the heat, even if we have a half-dry, half-wet race it will be challenging for all of us. But we are here to win."
The McLaren driver finished second behind his then team-mate Fernando Alonso in Malaysia in 2007.
Hamilton is expecting Ferrari to challenge strongly at Sepang after their poor start to the season Down Under.
Both Kimi Raikkonen and Felipe Massa failed to finish, although defending champion Raikkonen was classified eighth.
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"I expect them to be as strong as they were last weekend, but perhaps without the problems they had," Hamilton said.
"Hopefully they will have a better weekend. They cannot have a much worse weekend than they had last weekend. I am sure they will recover and do a better job. We will have to watch out for them."
Nonetheless, the team are focused on improving the car throughout the campaign ready for 2009.
"We already knew we were not close enough to fight for important things and we're well behind Ferrari, McLaren and BMW," said Alonso.
"We need to improve everything starting with the aerodynamics of the car, the efficiency of the car, more down-force, very normal things to be quick."
Alonso finished fourth in the season opening race in Melbourne but the Spaniard felt that was as much down to luck as it was performance.
"We were lucky with that situation. I would like to have wheel-to-wheel (battles) with a Ferrari or McLaren in a real race. So that is the real target for this season.
"For me, it's a bit like it was in 2003 and 2004 - you need to fight and close the gap and the races are a little bit more interesting for me because you are always in the middle of a group."
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