Jenson Button beat the showers that dogged second practice ahead of Sunday's Monaco Grand Prix to record the fastest time of the day.
With rain forecast as the session began, it forced all drivers to hit the principality street circuit to get in dry running before the dangers increased on a potentially greasy track.
After just 25 minutes, with the gloom closing in, the first light shower did enough to send the cars scurrying back into the pits. At that stage McLaren star Button held sway with a lap of one minute 15.746secs, a time that was never to be bettered as the rain drifted in and out, resulting in interspersed periods of activity and quiet.
Depending on which website you believe, there is the prospect of further rain over the weekend, but then the weather in such a microclimate as this part of the world is as unpredictable as the racing we have so far seen.
The rain played its part, but given there is no running on Friday in Monaco - a long-held tradition - the nature of the roads used for the race could alter considerably by qualifying on Saturday.
As in the first session, Lotus' Romain Grosjean was forced to settle for second best, initially to Ferrari's Fernando Alonso, and then Button, with the Frenchman 0.392secs adrift.
The Ferraris of Felipe Massa and Alonso finished third and fourth, the Brazilian for once this season ahead of his team-mate on the timesheet and under pressure this weekend to improve on his poor performances to date.
Race winner in Spain last time out, Williams' Pastor Maldonado, was fifth quickest a second down, followed by Nico Rosberg in his Mercedes.
Red Bull duo Mark Webber and reigning champion Sebastian Vettel were in seventh and 10th, the latter 1.5secs down, with Sauber's Kamui Kobayashi and Michael Schumacher in his Mercedes sandwiched between the pair.
Lewis Hamilton trailed in 11th, 1.6secs off his team-mate, with Force India's Paul di Resta narrowly behind his fellow Briton in 12th.