As afternoon becomes evening in Singapore, the storm clouds are gathering above the city street circuit.
As the experience of the past week has shown, any significant rain from now until the race-start at 8pm is likely to guarantee a wet track for the Grand Prix.
"The track dries incredibly slowly," observed Red Bull's Mark Webber. "It's something I haven't seen in my entire career."
Until late afternoon on Sunday, the sun had been shining in the Asian city-state's Marina Bay area.
But with three hours to go until race time, the skies have darkened, the wind is picking up, and there has been the odd drop of rain.
There is rain showing on the longer distance radar, but most paddock sources believe the race should be dry.
"If it does rain, the track will never dry out. It takes so long," agreed McLaren's Lewis Hamilton.