The first riders will leave the ramp in the heat of the early afternoon, while the last will be finishing as the sun sets.
The Under 23 men raced over the same distance and showed that the changing temperatures can have an impact on the result, and you could pay the price heavily for going out too fast.
Britain's Hannah Barnes is next to start. The Canyon rider is quickly into an aero position but takes the first long curve carefully.
Some riders have suggested that starting later, when temperatures are lower, will give an advantage. We will soon find out.
Many of the women have had a chance to race the course at full speed, and in the heat, during the team time trial on Sunday.
Rather than just one lap of the snake-like roads of the Pearl, the riders will do two, with the many corners and roundabouts playing an important role in the 28.9km time trial.
Ellen van Dijk is one of those former champions lining up in Doha.
Van Dijk looked set for a medal in the Olympic time trial, only to run off the road and be edged out for third place.
She has since won the European title and taking a second rainbow jersey would put the Olympic disappointment firmly to bed.
Van Dijk has already got one gold medal in her back pocket from the team time trial and the last time she did that, in 2013, she would go on to take the individual title a few days later.
Barnes sets the new fastest time at the first check point. She stopped the clock in 10:01.
Anastasiia Iakovenko (Russian) sets 10:18 but is slower than Barnes.
Barnes is riding at 47km/h as she hugs the barriers.
The only climb on the time trial course are the occasional bridges that join up the different islands of the Pearl.
Barnes is starting her second lap of the circuit.
Barnes was also fastest at the second time split, setting 18:11.
Julie Leith of Denmark is second fastest at 18:26.
The 2014 champion, Lisa Brennauer has come close on a few occasions although she is yet to win an individual time trial this season, but what a time to start.
The Germans have already had some success with gold and silver in the under 23 men’s event and Brennauer, who also won bronze in 2015, is certainly a contender to add another medal.
Trixi Worrack adds some serious firepower to Germany’s chances. The veteran rider showed she is a tough nut to crack when she claimed the national title just weeks after returning from a crash that resulted in her losing a kidney.
Barnes has an excellent position on the time trial bike, with only her hips moving slightly as she pushes on the pedals.
She uses the whole road on a curve to maintain as much speed as possible.
We stand corrected on the blocks of riders. The start list is divided into blocks of ten riders to avoid any problems on the circuit covered twice during the 28.9km course.
Varvara Fasoi (Greece) was the last to start of the first block. The second block will begin at 2:00pm local time, with Najla Aljeraiwi (Kuwait) first off.
Julie Leth of Denmark is the biggest threat to Barnes. She is seven seconds slower at the third time split.
As the women race for the world title in the time trial, most of the road racers have now arrived in Qatar and are enjoying a first training rider in the heat.
Here comes Barnes.
The talented British rider set a time of 39:00, making her fastest so far, ahead of Julie Leth (Denmark) who set 39:08.
Najla Aljeraiwi (Kuwait) kicked off the second block of riders. She is the sister of first starter Nada Aljeraiwi.
The Thailand rider Phetdarin Somrat started late after a rear wheel flat. Her staff tried to change wheels but eventually took her spare bike so she could start.
With the current temperature close to 39C the heat will be a huge factor today. Riders are warming up in the air conditioned tent at the start but also using ice jackets to keep their core temperature as low as possible.
Trixi Worrak (Germany) rolls out. She is a serious medal contender today.
Amber Neben and Carmen Small will shoulder the USA's hopes of a podium finish.
Both riders missed selection for the Olympic Games, despite taking the decision to arbitration.
Now 41, Neben won the world title in 2008 on a lumpy course in Varese. The course is probably better suited to US national champion Small, who claimed a bronze medal at the World Championships in 2013.
Annemiek Van Vleuten (Netherlands) starts with a huge ice pack under her jersey on her neck.
It's great to see Annemiek Van Vleuten racing at the world championships after her nasty crash in Rio.
Neben is also off, quickly pushing a big gear. She is last rider of the second block of riders.
Neben is fast and aggressive on the corners.
Barnes is in the hot seat as the fastest rider so far but Neben seems on course to beat here.
Worrack is also riding well. She sets 9:55 at the first time split, that's six seconds faster.
Neben sets 9:49. She is fastest so far.
Van Vleuten is also faster than Barnes but is 11 seconds slower than Neben.
Neben finishes her first lap in a time of 17:21, she's fastest by far.
She is the oldest rider in the race but is 21 seconds faster that Worrack.
Van Vleuten was third fastest after her first lap, 26 seconds slower than Neben.
Van Vleuten has lost a few seconds after the Thailand rider slowed her as she was caught. That could cost her a medal today.
She no doubt got a shot of anger from the incident, which could inspire her to push harder.
Worrack hits the third time split 44 seconds faster than Barnes.
Neben is faster than Van Vleuten with a time of 29:06.
Neben is pushing a huge gear with a slow but powerful cadence.
As the big names of the second wave finish, the third begins with Cecilie Uttrup Ludwig (Denmark) first off.
Neben's rear wheel slips slightly as she takes a corner at speed. She's taking plenty of risks.
Worrack finishes in a time of 37:48. She is fastest so far but not for long.
Van Vleuten sets 37:02 but her comes Neben.
Neben sets 36:37!
That's an average of 47km/h.
Neben won the world title in 2008 but could win it again this year.
It seems the wind has dropped as the light fades and the heat cools. It will be interesting to see if the conditions are the same for the final riders.
2013 winner Ellen Van Dijk is off next. She will know she faces a huge task to beat Neben.
2013 winner Ellen Van Dijk is off next. She will know she faces a huge task to beat Neben.
After leading early on, Barnes has slipped down to fourth fastest. She's had to give up the hot seat to Neben.
Van Dijk is using her power to stay on a similar schedule to Neben.
Van Dijk hits the first time split in 9:56 that's 6 seconds slower than Neben. She needs to find some extra speed from now on.
Britain's Hayley Simmonds is off the pace, she sets 18:49 at the split.
Van Dijk is taking risks on the corners, going through them at high speed.
Van Dijk finishes her first lap in 17:17.
That is 4 seconds faster than Neben. We have a real fight on our hands here.
Van Dijk is fighting hard now as the light fades and the temperatures cool.
Virtual times show Van Dijk leading by 4 seconds now. This will be very close.
Neben is watching nervously from the hot seat.
Uttrop of Denmark sets a time of 39:30 for sixth place so far.
Van Dijk gets out of the saddle to sprint and up the speed.
At the third time split Van Dijk sets 29:08, 2 seconds slower than Neben. She seems to be fading slightly.
on the straight sections of road, Van Dijk seems to be faster and pulls back several seconds.
Here comes Simmonds. She sets a time of 40:24.
The final block of riders are about to start. It includes some of the biggest names in women's racing.
32 Lotta Lepisto (Finland) 15:30:00 33 Karol-Ann Canuel (Canada) 15:31:30 34 Ashleigh Moolman-Pasio (South Africa) 15:33:00 35 Carmen Small (United States Of America) 15:34:30 36 Ann-Sophie Duyck (Belgium) 15:36:00 37 Alena Amialiusik (Belarus) 15:37:30 38 Katrin Garfoot (Australia) 15:39:00 39 Olga Zabelinskaya (Russian Federation) 15:40:30 40 Lisa Brennauer (Germany) 15:42:00 41 Anna Van Der Breggen (Netherlands) 15:43:30
Elena Cecchini (Italy) finishes in a time of 39:07, that's fifth fastest so far.
Pawloska of Poland goes one spot better, finishing fourth, with 38:13.
Here comes Van Dijk.
She fails to beat Neben. She set 36:43, six seconds slower.
She seemed to crack in the final 500 metres and struggled to push her huge gear.
Katrin Garfoot (Australia) is off next, with Anna Van Der Breggen (Netherlands) off last of the 41 riders.
Garfoot has a Camelbak to stay hydrated and perhaps give her a slight aerodynamic edge.
Olga Zabelinskaya (Russia) also starts her ride.
RT @WMNcycling: Strong finish for @ElenaCecchini92 in 39:07
Van der Breggen rolls down the ramp. She is last to start. In 36 minutes we will find out if she is world champion.
The 26-year-old has had a superb season, winning the road race at the Olympic Games and going on to claim silver in the time trial.
Amialiusik sets 10:04 -sixth at the first split.
The shadows are lengthening as the afternoon becomes evening in Qatar.
Carmen Smalls (USA) is also out on the course, she was 12 fastest at the first split in 10:18.
Zabelinskaya is only fifth at the split, 10 seconds slower.
American @amberneben still leading. Van Dijk didn't beat her time at +6 sec. Carmen Small @smallsunday now out on course and looking fast.
1 Amber Neben (United States of America) 36:37:04 2 Eleanora Van Dijk (Netherlands) 00:00:05 3 Katrin Garfoot (Australia) 00:00:08 4 Olga Zabelinskaya (Russian Federation) 00:00:11 5 Annemiek Van Vleuten (Netherlands) 00:00:25 6 Lisa Brennauer (Germany) 00:00:57 7 Trixi Worrack (Germany) 00:01:11 8 Ann-Sophie Duyck (Belgium) 00:01:27 9 Katarzyna Pawlowska (Poland) 00:01:36 10 Alena Amialiusik (Belarus) 00:01:41
It's been a hugely successful day for USA riders, with Brandon McNutly winning the junior men's title.
Neben admitted that it had been a tense and nervous time in the hot seat as she waited for the other riders to finish.
"It was a long wait, I think I used more energy sitting there waiting than I did on the bike," she said.
"Traditionally I am a pretty steady rider, I'm not real fast in the beginning so I try to just sustain it and be steady. The difference I think was the mental perseverance, to have that extra power to finish strong."
"I was so nervous, it was so hard to watch. I feel for Ellen, having been second, third, fourth places, but at the same time I'm so excited to be able to hold on."
"I think this one is more special because of everything that's happened between 2008 and now. There have been so many things I've had to persevere through. Just the struggle and being resilient and persevering, getting up and not giving up. I'm speechless."
Neben is awarded her gold medal and rainbow jersey by UCI vice-president David Lappartient.
He has confirmed that he will not stand for the role of president of the French Federation. Instead he is expected to stand as a rival of Brian Cookson for he role of President.
Neben stands, hand on heart as the US national anthem rings out across the podium area.
This is the first image of Amber Neben on her way to victory in the time trial world championships.
For full results, photos and race report, click here.
Thanks for joining us for our full live coverage from the World Championships.
We'll have full coverage of the elite men's time trial on Wednesday.
Cross-country tyres are the lightest and fastest MTB rubber. You need to be able to finish if you're looking to finish first though and race conditions can really vary too
