It will be hot work for the peloton in the Tour de France as temperatures hit the 40 degrees mark this week AFP/JEFF PACHOUD

NIMES, France: With the action on the Tour de France already red hot, Geraint Thomas and his challengers for ultimate victory are bracing for a head-on collision with a heatwave bearing temperatures of 40 degrees Celsius (104 Fahrenheit) and above over the next three days.

That coincides with three mountain stages in the Alps that test top riders at the best of times but will probe the outer limits of endurance in a heatwave.