Lewis Hamilton topped the times in second practice for the Monaco Grand Prix before the rain rendered most of the session useless.
The rain hit the circuit some 25 minutes into the 90-minute session, and no driver managed to complete a timed lap with the super-softs tyres.
Hamilton's best of 1:17.192 was enough to keep him on top of the times from teammate Nico Rosberg, who was over seven tenths slower than the world champion.
The Toro Rossos were again very competitive, finishing sixth and seventh with Carlos Sainz and Max Verstappen.
Fernando Alonso (McLaren), Romain Grosjean (Lotus) and Nico Hulkenberg (Force India) completed the top 10.
Rosberg wasted no time and was one of the very first drivers to take to the track, setting the early benchmark before he was outpaced by Raikkonen, who went quickest before going wide at St Devote.
The Finn was soon relegated down the order by Vettel, Felipe Massa and the impressive Verstappen before Pastor Maldonado brought out the yellow flags when he had to take the escape road at Mirabeau, an incident mirrored by Vettel moments later.
Ten minutes in, Hamilton returned to the top with the fastest time of the weekend at that point: a 1:17.640, but improved by nearly half a second on the following lap despite some lock-ups during the lap.
The session was red-flagged after 15 minutes when Roberto Merhi lost control of his Manor at the exit of the tunnel, crashing against the right-side wall.
Merhi was uninjured, but his car suffered damage to the front wing.
As the drivers waited for the track to be cleared, however, rain hit the circuit and the action came to a stop.
Maldonado was the only driver who braved the conditions as he attempted a super-soft tyre run. But the Lotus driver had to return to the pits right away as the rain intensified.
There was no track action whatsoever until the final 10 minutes, when some drivers ventured out with intermediate tyres, but lapped ways off the pace.
Sauber's Marcus Ericsson was the only driver not to complete a lap, the Swede hit by a mechanical issue.
|Pos||Driver||Car / Engine||Time||Gap||Laps|
|5||Daniil Kvyat||Red Bull/Renault||1'18.548||1.356||16|
|6||Carlos Sainz||Toro Rosso/Renault||1'18.659||1.467||14|
|7||Max Verstappen||Toro Rosso/Renault||1'18.782||1.590||12|
|9||Nico Hulkenberg||Force India/Mercedes||1'19.151||1.959||13|
|11||Sergio Perez||Force India/Mercedes||1'19.300||2.108||13|
|16||Daniel Ricciardo||Red Bull/Renault||1'19.639||2.447||13|