Lewis Hamilton has been left on the back foot in pre-season testing after he missed a full day of running in Barcelona.
The defending Formula 1 world champion had been scheduled to take to the wheel of his Mercedes at the Circuit de Catalunya on Tuesday afternoon before his team changed their minds.
Hamilton completed only 25 laps here on the opening day, and with snow forecast for Wednesday, there is every danger the Briton could miss out on further valuable mileage.
There are only eight full days of testing before Hamilton opens the defence of his championship in Melbourne on March 25.
Hamilton, 33, has complained about the tedium of practice in the past, and has cited illness as a reason to withdraw from a handful of tests in recent years.
But Mercedes say they did not want to waste minutes swapping their drivers around after losing track time in the morning following the cold conditions. The regular one-hour lunch break was also scrapped due to the poor weather.
Hamilton's motorhome is parked adjacent to the Mercedes' hospitality suite in the paddock, and he remained at the circuit despite his non-track appearance.
Mercedes say he was willing to go along with their decision to give team-mate Valtteri Bottas an entire day of running.
"Valtteri Bottas will continue to drive to maximise our mileage after the poor track conditions limited running this morning," Mercedes tweeted.
"Mileage is king in F1 testing, so we want to make the most of the current conditions. A driver swap would require switching seat, pedals, even stickers when we could be out on track."
While Hamilton is scheduled to run on Wednesday, the threat of snow and rain could make it a complete washout with teams unlikely to run the risk of damage to their cars.
"I didn't really get the chance to push in the car and go up to top speeds as the conditions were so bad," Hamilton said as he reflected on his short run-out on Monday.
"It's hard for me to say a whole lot about the car because I did not drive it for a long time, but the initial feeling is good."
In Hamilton's absence, Bottas completed 94 laps, four fewer than Ferrari's Sebastian Vettel, who topped the time sheets after he became the first driver to dip beneath the one minute 20 seconds mark this week.
Despite times being largely irrelevant at this stage of the season, Vettel finished 0.303secs clear of Bottas with McLaren's Stoffel Vandoorne an encouraging third in the order.
The British team have been desperately off the pace in recent seasons, but hope their switch from Honda to Renault engines will propel them up the grid.
Vandoorne, who completed all of his laps in the morning, finished ahead of Red Bull's Max Verstappen, who was fourth.
Robert Kubica, the Pole whose career was halted following a harrowing rally crash, took part in his first pre-season test for seven years. The Williams reserve driver managed 46 laps and was seventh fastest.