Regular rain is forecast for the entire Belgian grand prix weekend.
"The weather is always something we talk a lot about when we go to Spa-Francorchamps," said Force India’s Tonio Liuzzi.
Rain is traditionally regular and unpredictable in the Ardennes forest region.
"Rain can come at any time and, as the track is so long, you can have some parts of the circuit wet and others dry," added the Italian.