We'll definitely take that error on the first stage! Here is Cavendish's average speed:
Stage 1: 12.33 m/s (44.39 kph or 27.59 mph)
Cavendish will don the yellow jersey for tomorrow's 183-km (114-mi) Stage 2. The hilly stage begins in the commune of Saint-Lô, moves south, then southwest, before turning north along the coast toward the commune of Cherbourg-en-Cotentin. Our prediction is given below.
Stage 2: 4h 22' 59" (prediction)
There are three category 4 climbs early on and a category 3 climb to finish the stage. Will Cavendish be able to enjoy his first yellow jersey for more than a day?