MENDE, France - If tackling 3,600km of road including seven mountain stages over three weeks wasn't hard enough, the weather has proved to be the toughest challenge at the 2015 Tour de France.
The Tour began with a heatwave in Utrecht two weeks ago and since then has been hit by crosswinds and driving rain as early as the second stage to Zeeland, when overall contenders Vincenzo Nibali and Nairo Quintana lost a minute and a half to Chris Froome and Alberto Contador.
Wind and rain were the main harbingers of doom during the Tour's first week but since the peloton reached the Pyrenees last Tuesday, it has been suffocating heat that's been their worst enemy.
Temperatures started in the mid-30s Celsius but soared up to 40 degrees (104 degrees) Fahrenheit.
Both Nibali and Contador have complained of being "unable to breathe" on the climbs.
On Friday a near-record roadside temperature of 61 degrees was noted - the record is 63 degrees from 2010.
And if the heat wasn't bad enough, on Thursday riders started in stifling conditions before ending the stage in Plateau de Beille just after a terrific thunderstorm had battered the finish with lightning, hail and driving rain for two hours, dropping the temperature from 38 degrees to 12 degrees in a matter of minutes.
Many riders have suffered, mostly from the heat, with the likes of Spain's Joaquim Rodriguez, French trio Jean-Christophe Peraud, Thibaut Pinot and Romain Bardet, all seeing their overall hopes go up in smoke in the Pyrenees as the mercury rose.
'heat is a mountain'
Pinot suffered so badly on Wednesday that he finished in a first group more than 21 minutes behind stage winner Rafal Majka, having finished third behind Nibali and Peraud 12 months ago.
"I've come to realise these last few days that as soon as it gets hot, I quickly lose energy. The heat is a mountain," said the 25-year-old.
After Friday's stage, race leader Froome revealed the logistical difficulties of racing in 40-degree heat.
"Every 10 to 15 minutes you have to take more water from the car," he said.
FDJ said their riders took on average 20 bottles each from the car during the 4hr 43min stage.
Riders and their teams are used to managing extreme heat, though, and know how to deal with it, even if their bodies don't always respond as they'd like.
Lotto-Soudal team doctor Jan Mathieu says a rider will lose 10 percent of his strength for every 1 percent of his body weight he sweats out, therefore rehydration is vital.
"A sportsman who weighs 70kg and loses almost three litres of water during his effort loses 40 percent of his strength," he said.
"The rule is to drink two bottles per hour, that's one litre." One issue, though, is not just the loss of water but the associated loss of salts and minerals.
German sprinter Andre Greipel tweeted a picture of himself following Wednesday's stage showing his salt-stained shorts from the amount of sweat he'd lost.
"Somebody needs salt? Have plenty of natural biological gained salt...for free of course..." he joked.
Two days later, though, he wasn't seeing the funny side any more.
"Don't want to complain but I am really asking myself where the line about extreme weather condition is @UCI-cycling?" he tweeted.
Belgian rider Jan Bakelants has a simple, if unappealing, solution for salt-loss problems.
"I always dilute one or two coffee spoons of salt in my water bottles," he said.
Australian Michael Matthews keeps cool by dousing himself with water but said that "once you start, you can't stop" as the body constantly craves more.
But not everyone is complaining, least of all the race leader.
"Some guys feel better in the cold and some guys feel better in the heat," said Briton Froome, who was born in Kenya and grew up in South Africa.
"For me, I prefer really hot weather, but that's bike racing for you, you've got to be able to race with everything.