GP3 championship leader Valtteri Bottas set the pace in free practice at Spa on Friday morning.
The ART Grand Prix driver moved to the top of the times early in the session, and he was still there when the first rain shower of the weekend hit with 11 minutes remaining.
Shortly before the rain fell, MW Arden's Mitch Evans had been chipping away at the Finn's margin out front. He initially brought it down from 0.9 seconds to 0.6, and he chopped it down to 0.2s with his final flying lap.
James Calado was third in the second ART entry, just ahead of Adrian Quaife-Hobbs (Manor) and Antonio Felix da Costa (Status).
Nigel Melker had been Bottas's closest challenger early on, but the RSC Mucke driver slipped to sixth while the times were improving.
Just behind him was Alexander Sims, who currently sits second in the championship. The Status Grand Prix driver was one of the few to stay out on slick tyres when the rain initially fell, and he was only lapping 9s off the pace before the showers got heavier for the final couple of minutes.
Evans was one of the first to venture out on wet weather rubber, but he returned to the pits without completing a flying lap.
GP3 will not have a second practice session this weekend, as the circuit's noise curfew means the on-track action has to finish earlier than at other races. As a compromise, this morning's session was extended to 45 minutes instead of the usual half an hour.
Pos Driver Team Time Gap 1. Valtteri Bottas ART 2m14.546s 2. Mitch Evans MW Arden 2m14.826s + 0.280s 3. James Calado ART 2m15.093s + 0.547s 4. Adrian Quaife-Hobbs Manor 2m15.274s + 0.728s 5. Antonio Felix da Costa Status 2m15.343s + 0.797s 6. Nigel Melker RSC Mucke 2m15.492s + 0.946s 7. Alexander Sims Status 2m15.495s + 0.949s 8. Simon Trummer MW Arden 2m15.510s + 0.964s 9. Michael Christensen RSC Mucke 2m15.733s + 1.187s 10. Ivan Lukashevich Status 2m15.851s + 1.305s 11. Mattias Laine Manor 2m15.917s + 1.371s 12. Lewis Williamson MW Arden 2m15.931s + 1.385s 13. Nick Yelloly Atech CRS 2m15.957s + 1.411s 14. Aaro Vainio Tech 1 2m16.013s + 1.467s 15. Tom Dillmann Addax 2m16.015s + 1.469s 16. Rio Haryanto Manor 2m16.038s + 1.492s 17. Marlon Stockinger Atech CRS 2m16.203s + 1.657s 18. Tamas Pal Kiss Tech 1 2m16.205s + 1.659s 19. Zoel Amberg Atech CRS 2m16.245s + 1.699s 20. Conor Daly Carlin 2m16.429s + 1.883s 21. Richie Stanaway ART 2m16.453s + 1.907s 22. Nico Muller Jenzer 2m16.614s + 2.068s 23. Dean Smith Addax 2m16.833s + 2.287s 24. Callum Macleod Carlin 2m17.002s + 2.456s 25. Gabby Chaves Addax 2m17.037s + 2.491s 26. Maxim Zimin Jenzer 2m17.044s + 2.498s 27. Alex Fontana Jenzer 2m17.277s + 2.731s 28. Daniel Mancinelli RSC Mucke 2m17.385s + 2.839s 29. Leonardo Cordeiro Carlin 2m17.524s + 2.978s 30. Thomas Hylkema Tech 1 2m18.755s + 4.209s