FTP With relation to temperature?

What is the relation between FTP or any other Critical Power KPI for that matter with Temperature?

To be more specific -
Assuming I know my FTP which was obtained while training for a long period in a 20C (degrees) environement and I use that information to manage myself in a race.
So far so good.
Now I want to use this data to do an identical race but in a 40C (degrees) environment.
Logic predicts that I won’t be able to achive same results because my body is not prepared for such heat and I assume I won’t be able to hold the % of power I’m used to per my FTP.
So what good is it to know and quote the FTP value without expressing alongside other effecting parameters of the environment (or other) in which it was obtained?
I hope my question is understood.

I’ve never seen a strict numerical relationship between FTP and temperature like I have for altitude. I’m sure it exists but I imagine it would be very individual.

But it would probably be better to just use RPE to gauge your effort while making an concerted effort to take in more water and salt.

This is also why it’s never very useful to compare FTPs between people. I could do 300W at sea level in 85f and 80% humidity while you might do 300W at 5000ft, 60f and 20% humidity. How would you adjust those values to make up for the difference in altitude, temperature, and humidity. But to compare for 1 person across many environments it comes down to either you have to frequently go to that other environment to see how you react or you just pace conservatively and the use RPE to gauge your effort.

Thanks. That is what I thought.
So any Performance Predictor tool that requires you to enter your FTP in order to predict your race result is quite useless if it doesn’t also know the environment data in which it was obtained.
For example BestBikeSplit.com - claims that “…Our math and physics engine takes your power data, course info, and race day conditions to predict your race performance and create the perfect power plan so you can hit your best bike split ever…” - but as you say - my power data is only with a specific relation to the environment where it was tested and measured. So I’m guessing that the outcome prediction will not be so accurate.

Yeah I don’t know for sure what ‘race day conditions’ BBS takes into account. I know they use wind speed and direction but I’m sure they also use temperature, humidity and pressure for the purposes of aerodynamics but I don’t know if they apply that to your ability to output power.


Not scientific but I did an hour long TT in 30deg this year and my FTP was down 12.8%.

Even if they do, it all comes down to - how do they know what is the ‘base’ index in which they need to adjust it correctly. Because as you stated 300W FTP which was achieved by someone at sea level in 85f and 80% humidity is different to a 300W FTP obtained at 5000ft, 60f and 20% humidity (assuming same weight, physics etc).

I don’t think FTP really should be used for any such purpose. Your FTP can help you set your workout power targets. But rarely, if ever, is FTP going to be applicable to an event.


I imagine that is pretty individual. I haven’t noticed a correlation to my FTP and heat. I routinely ride in 40* C weather in my area.

Everyone will respond slightly differently to extreme temperatures. Without testing yourself in those conditions then it would be impossible to predict.

Around here summer afternoons are 32-38C (90-100F), and I see a drop when temps first increase in May. After acclimatizing to heat - about 3 weeks - I mostly back however on hot days, and speaking as a polar bear, I do find it helps to carve up long tempo/sweet spot/threshold intervals into shorter intervals with 1-3 minutes recovery.

There are various studies on acclimating/acclimatizing, and most people return to fitness level once the body has time to adjust to the heat.

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I would imagine that a block of training at similar temperatures/conditions would help with the adaptation. FTP is merely there to train in those extreme conditions and let the body adapt to it.

:thinking: it is relevant to all of my weekly Wed night worlds… and all my climbs into the Sierra and Coastal mountains, and the time trials I do. My FTP reflects what I can do for 35-70 minutes depending on the level of muscular endurance and mental toughness.

Now in the heat? After acclimating I can usually train in 32-35C / 90-95F dry heat using FTP as basis for workouts from endurance to threshold.


A key issue is how well acclimated you are to the heat. Someone who is acclimated to the heat will see a smaller drop-off than someone who isn’t.

Just because you usually ride in 20C, doesn’t mean you can’t acclimate yourself to heat. Some options that may be available include:

  • turning off the fan for your indoor training
  • wear your winter kit
  • relocate your trainer to the bathroom (especially for humidity adaptations)
  • if you usually go for a (cool) dawn outside ride, try riding at lunchtime instead
  • use a sauna

You don’t have to do all your training like this. Generally acclimating to heat takes 2 weeks, so you can do this while tapering for your A event. Or still do your key workouts in cool conditions at maximum power, but try acclimating during endurance intensity rides.

I don’t think temperature is that important, humidity and cooling are. If it is hot and arid, I think it is much easier on you — provided you stay on top of your hydration. A little bit of wind or a high average speed also help with evaporative cooling. When it is humid, it gets tougher.

But to be honest, I don’t think you need to do dedicated heat training. Just pace conservatively if it is hot and humid, listen to your body and stay on top of your hydration. If your RPE goes through the roof, lower your power, you competitors are likely going through the same thing, too.

As far as a neat formula goes, I don’t know of any. But I reckon that the variability is too large for there to be one that reliably predicts that relationship anyway. You will know if you are going too hard. And since your competitors are in the same boat as you, they’ll likely have to shift down a gear when you have to, too.

Rather than looking at your FTP, I’d also adapt my race tactics. I did my only race this year during the hottest weekend of the year. I live in Japan, so hot equals humid. Initially, I wanted to attack right after the prime lap and try to TT. But it was so hot that I thought it wasn’t worth it. This was my first crit race anyway, so I had plenty of other things to learn. Indeed, two athletes suffered from a heat stroke that was severe enough to require hospitalization. Our team captain was smarter, he pulled the plug during his race and was completely exhausted.

My FTP reflects what I can do for 35-70 minutes depending on the level of muscular endurance and mental toughness.

This is the best explanation of FTP I have read. I don’t want to turn this into one of those threads, but I think this definition is most useful for most people/circumstances.

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