Mercedes’ Lewis Hamilton set the pace during the second practice session for the Belgian Grand Prix, before rain fell at Spa-Francorchamps.
Hamilton held a substantial advantage after the initial laps, which he completed on Soft tyres, and preserved a comfortable buffer after the field switched to Ultrasofts.
Hamilton’s lap of 1:44.753 was 0.262s quicker than Ferrari’s Kimi Räikkönen, who clocked the fastest time during the morning session.
Valtteri Bottas finished third for Mercedes while Red Bull's Max Verstappen still took fourth despite locking up into La Source.
Ferrari’s Sebastian Vettel was fifth, with the leading quintet covered by less than half a second, as Daniel Ricciardo finished a distant sixth for Red Bull.
Ricciardo, after an earlier problem, carried out his Ultrasoft run later than his rivals, and was unable to challenge for a higher position.
Light rain began to fell with half an hour remaining in the session, and conditions quickly deteriorated, with the rain intensifying.
Only Ricciardo and McLaren’s Fernando Alonso appeared for a brief exploratory lap on Intermediates, and cruised around the circuit at very slow speed as the deluge continued.
Renault’s Nico Hülkenberg led a tightly-congested midfield group, with a handful of drivers from different teams separated by just a few tenths.
Hülkenberg edged out Force India’s Esteban Ocon, Toro Rosso’s Carlos Sainz Jr., Renault team-mate Jolyon Palmer and McLaren's Alonso, the gaggle covered by three-tenths of a second.
Sergio Pérez finished in 12th position, in front of Romain Grosjean, as both Haas drivers recovered from early DRS issues.
Grosjean and team-mate Kevin Magnussen, who placed 16th, appeared on track with the DRS stuck open, prompting them to return to the pits, but the squad was able to swiftly rectify the defect.
Magnussen was also involved in a bizarre incident with Perez as he moved over on his rival, appearing to block the Force India driver, as they exited the left-hander at Liege.
Grosjean and Magnussen sandwiched McLaren’s Stoffel Vandoorne and Toro Rosso’s Daniil Kvyat, while Williams’ Lance Stroll took 17th.
Sauber again finished significantly off the pace, with Marcus Ericsson once more in front of Pascal Wehrlein.
Williams' Felipe Massa did not run due to his crash in the opening practice session, which required a change of chassis.
As Massa’s car needs to be re-scrutineered, he was unable to take to the circuit, meaning he will enter Saturday’s action with just two laps under his belt.
