Bad weather could affect the start of winter testing in Barcelona this week.
The action kicks off on Monday, and the forecast for the next few days around the Spanish city is for cold conditions, some rain - and perhaps even snow.
"It should be cold," agreed Ferrari's Sebastian Vettel.
"I don't know how much we will learn."
The F1 world always studies winter test laptimes closely, but Mercedes technical boss James Allison warned against that.
"It's never easy to do your tyre homework in Barcelona," he said.
"First, it's usually cold. Secondly, the circuit has recently been resurfaced, which distorts the comparative data from previous years.
"But the situation is the same for everyone."
The season proper gets underway in a month's time with the Australian Grand Prix.