The 99th Tour de France gets down to business on Tuesday when light rainfall and strengthening winds are likely to face the peloton on an extremely hilly run-in to the French fishing port of Boulogne-sur-Mer. Unlike last Sunday’s stage 1, where all the drama took place in a couple of minutes on the finishing climb to Seraing, this stage 3 has five steep hills coming one after the other in the final 60 minutes, including a steep 700-meter-long ramp to the line.

The climbs, with double-digit-percentage grades on three of them, are sure to split up the peloton, while constant changes of direction in the predicted 20-kph crosswinds will make the finale even tougher. This coastal region of Picardy is familiar to pro cyclists, with the area’s exposed chalky hills a constant challenge at May’s Four Days of Dunkirk stage race. And last year’s French national championship was held on a circuit that finished on the same Boulogne hill, crowned with a brilliant solo attack by Sylvain Chavanel, who’s one of the favorites to win on Tuesday.

Besides the race for the day’s podium—which might go to Sunday’s winner Peter Sagan of Liquigas-Cannondale or that day’s fourth-place finisher Philippe Gilbert of BMC Racing—this stage 3 will also see a sifting out of the overall contenders. Gilbert’s BMC team leader Cadel Evans says he’s ready to take on whoever wants to challenge him for his Tour title, and he may well have to race his hardest to parry the expected thrusts from his top opponents.

And if the forecast rain really does come, then crashes will likely dramatize the racing on the tricky downhills. Evans, the former mountain biker, is totally comfortable racing in the rain and hills, and he could well take time out of the less-adept men such as hot race favorite Brad Wiggins of Team Sky. I can remember a wet day early in the 1992 Tour when the Evans-like Greg LeMond broke away with Frenchman Laurent Jalabert, Italian Claudio Chiappucci and Dane Brian Holm on a hilly finale into Brussels, where defending champion Miguel Induráin, who hated the rain, lost 1:22 to his rivals.

So who might come through this time, besides Evans, Gilbert and Sagan? The obvious candidates are men who do well in the hillier spring and fall classics. Among these are Chavanel (who could help his Omega Pharma team leader Levi Leipheimer pull back some of the 38 seconds he has lost to Wiggins so far), Italian dark horse Michele Scarponi of Lampre-ISD, Luxembourg’s Fränk Schleck (and his RadioShack-Nissan teammate Fabio Cancellara, the race leader), Canadian Ryder Hesjedal of Garmin-Sharp (and his teammate Christian Vande Velde), Italian hope Vincenzo Nibali (Sagan’s team leader), and perhaps Spain’s Samuel Sanchez of Euskaltel and Alejandro Valverde of Movistar.

As for Wiggins, should the conditions turn nasty, he will have to rely heavily on his Sky teammates Eddy Boasson Hagen, Richie Porte and Bernhard Eisel. If the early sunshine persists on Tuesday then the stage will still be spectacular but far less decisive. The true contenders know that this Boulogne stage is the first tough test of the 2012 Tour, and the only difficult one before next weekend’s double assault, with a severely steep summit finish in the Vosges on Saturday and a succession of gnarly climbs into Switzerland on Sunday.

So far, this Tour has just been eye candy: some pretty nice wins but no real substance. There was a predictable prologue win for the too-powerful Cancellara, a just as expected uphill success for the cherubic Sagan, and a scintillating sprint victory for Superman Mark Cavendish. Now it’s time for the real Tour contenders to unsheathe their weapons and start the real battle for the maillot jaune.