Ferrari's Fernando Alonso topped the times in Thursday's rain-restricted second free practice ahead of Sunday's Monaco Grand Prix.
The 32-year-old Spaniard clocked a best lap of one minute and 18.482 seconds to finish fastest, in a brief flurry of 15 minutes' late 'dry weather' action, ahead of championship leader Lewis Hamilton of Mercedes.
But Hamilton was fastest overall for the day, having clocked a best lap of 1:18.271 in the morning when he and Mercedes team-mate German Nico Rosberg dominated the session.
Two-time champion Alonso recorded his best lap in the brief dry run in the afternoon with 1:18.482 ahead of Hamilton on 1:18.901.
They were the only two to dip below the 1:19 barrier in the afternoon session.
Defending four-time champion Sebastian Vettel of Red Bull was third ahead of Jean-Eric Vergne in his Toro Rosso car and Valtteri Bottas of Williams.
After a heavy downpour during the interval before second practice began, the track was left so wet that most of the field declined to venture out for 45 minutes or more.
When a few drivers led the way only a handful followed and with 20 of the 90 minutes remaining, the action was limited to a few laps set by the two McLaren men, Vettel and Raikkonen.
The Finn was one of the first out, but suffered a gearbox problem that left him stuck in third and forced him out of the session leaving Button on top ahead of Vettel and Alonso.
Hamilton, who was fastest ahead of Rosberg in the morning session, delayed his participation until 15 minutes from the end when he went out on intermediate tyres.
At that stage, the track was still damp and potentially treacherous.
Venzuelan Pastor Maldonado of Renault said: "It's been a bit boring, but we're just waiting for the track to dry. We want the best conditions.
"It's quite risky and, in my opinion, it's not important to be out on track on the intermediate or full wet tyres."
His views appeared to represent the majority of a pit lane that saw little point in taking risks in tricky conditions when dry weather has been forecast for Saturday's critical qualifying session.
With ten minutes remaining, only nine of the 22 drivers had set a time, but in a final flurry of action - as the track dried in warm sunshine - all of the remaining drivers went out on the 'supersoft' tyres to gain experience and data ahead of Saturday.
Vergne, followed by Hulkenberg and then Alonso set fastest times as the leaders trimmed their best efforts in the final seconds.