Jenson Button was quickest in Thursday afternoon practice for the Monaco Grand Prix, as all the leading positions were set in 15 minutes of early dry running before showers intervened.
All the teams were expecting rain to feature in practice two, which meant a rush of early runs prior to the first precipitation arriving a quarter of an hour in.
By that time, Button's McLaren was on top with a lap in 1m15.746s, 0.392 seconds clear of second-placed Romain Grosjean's Lotus.
The Ferraris of Felipe Massa and Fernando Alonso were next up, with Barcelona winner Pastor Maldonado completing the top five for Williams.
Championship leader Sebastian Vettel's Red Bull was back in 10th.
The rain did briefly ease around the half-hour mark, encouraging a few drivers to come back out on slicks, but conditions were far from good enough for quick times, and a second shower came soon after. Although the track dried out again towards the end, even with nearly the full field on the circuit at times, a truly dry line never emerged.
Despite the slippery conditions, everyone managed to avoid the barriers. There were plenty of trips down escape roads, with everyone managing to continue except Heikki Kovalainen, who could not get his Caterham's reverse gear to cooperate after sliding off at Mirabeau.
Pos Driver Team Time Laps 1. Jenson Button McLaren-Mercedes 1m15.746s 14 2. Romain Grosjean Lotus-Renault 1m16.138s + 0.392 17 3. Felipe Massa Ferrari 1m16.602s + 0.856 19 4. Fernando Alonso Ferrari 1m16.661s + 0.915 21 5. Pastor Maldonado Williams-Renault 1m16.820s + 1.074 18 6. Nico Rosberg Mercedes 1m17.021s + 1.275 13 7. Mark Webber Red Bull-Renault 1m17.148s + 1.402 21 8. Kamui Kobayashi Sauber-Ferrari 1m17.153s + 1.407 20 9. Michael Schumacher Mercedes 1m17.293s + 1.547 9 10. Sebastian Vettel Red Bull-Renault 1m17.303s + 1.557 19 11. Lewis Hamilton McLaren-Mercedes 1m17.375s + 1.629 17 12. Paul di Resta Force India-Mercedes 1m17.395s + 1.649 19 13. Bruno Senna Williams-Renault 1m17.655s + 1.909 18 14. Nico Hulkenberg Force India-Mercedes 1m17.800s + 2.054 23 15. Sergio Perez Sauber-Ferrari 1m18.251s + 2.505 22 16. Vitaly Petrov Caterham-Renault 1m18.440s + 2.694 23 17. Jean-Eric Vergne Toro Rosso-Ferrari 1m18.522s + 2.776 20 18. Daniel Ricciardo Toro Rosso-Ferrari 1m18.808s + 3.062 24 19. Kimi Raikkonen Lotus-Renault 1m19.267s + 3.521 23 20. Timo Glock Marussia-Cosworth 1m19.309s + 3.563 27 21. Heikki Kovalainen Caterham-Renault 1m20.029s + 4.283 13 22. Charles Pic Marussia-Cosworth 1m20.240s + 4.494 19 23. Pedro de la Rosa HRT-Cosworth 1m20.631s + 4.885 12 24. Narain Karthikeyan HRT-Cosworth 1m20.886s + 5.140 10 All Timing Unofficial