Am I the only one struggling to finish a race in the heat? This past week its been 29 degrees in the room I have my trainer. My Zwift Hub has dropped out a couple of times, is blisteringly hot to the touch, and I’m missing about 10% of usual power.
Daft question, but is this a physiological issue, an equipment issue, or mixture of both.
Peaked at 31 indoors for me on Monday and gave up trying to ride.
I’d say it’s definitely going to be physiological, but worth contacting support about the trainer too.
My laptop struggles in that sort of heat too.
Many find they produce less power for a given heartrate when they return to the turbo after a summer break and it will likely take a few weeks of harder sessions/races to acclimatise (get similar power output for given bpm) while using fans and drinking a lot more than outdoors.
Heatwaves take it to another level and the heatwave might end before your body adapts.
Been horrid this last past week, approx 30C outside and very near that indoors! 
As somebody who got heat exhaustion whilst riding once i can say that heat can have a dramatic effect on performance.
Can’t remember the stats but it only takes a handful of % decrease in your body’s hydration level before it seriously affects performance.
Hallucinations and ultimately death is surprisingly close too.
Thanks for the replies, this is reassuring that I haven’t suddenly got worse.
But also since I don’t fancy the idea of the side effects Stuart points out, it looks like I’ll have to pair back my summer racing or only race evenings on cooler nights.
More outdoors Zone 2 for me for a while.
Portable AC unit would help for the 2 weeks a years it’s too warm.
Have one in the bedroom. Absolute Godsend.
Darwin Award incoming.
I’ll take it in the form of a virtual trophy please 
Heat acclimation is possible but it takes some steady aerobic training time for a couple few weeks
Jumped on Constance yesterday for my usual 100k slam but i could barely hold wheel for 10 mins and gave up as it was so damn hot in my gym, the fans just blowing hot air in my face…just couldnt do it.
Here’s a link to page with the stats i was referring to.
Thanks Stuart. Interestingly I did weigh myself before and after and lost 2 lbs, or approx. 1 litre of water. Yikes!
Here’s a good summary from FasCat Coaching…
The Science: Your body is always trying to maintain equilibrium, and heat can significantly disrupt that. Heat comes from metabolism and needs to be dissipated through the skin or breath. When the ambient temperature is too hot, it limits the body’s cooling and can raise core body temperature. Core body temperature is the central governor of exertion in the human body; get too hot and the brain exerts protective measures to slow the body down.
The Performance: The optimum ambient temperature for cycling is around 50-65 degrees. The further you get from this range, the more your performance suffers. High heat affects metabolic efficiency and stresses the body’s cooling processes (such as sweat rate, vasodilation/constriction of non-active muscle, and cardiac efficiency via stroke volume changes) that indirectly impact power output. Similarly to the effects of altitude, there is a curvilinear decline in power as temperatures exceed about 80 degrees. That can be lessened with acclimatization but never completely mitigated.
The Practical: It takes your body 10-14 days to adapt to high heat. During this time your body is increasing blood plasma volume and altering its sweat sodium concentration, diluting your sweat so that you can take better advantage of evaporative cooling. During this acclimatization phase it’s important to hydrate consistently throughout the day and with cool drinks on rides, plus hyper hydrate before and after sleep.
How to Acclimate: Very few of us — even top professionals — can afford to spend two weeks at a race location to acclimatize, but there are other effective solutions. Overstressing the body to adapt to heat is something lots of cyclists and multisport athletes do. Sauna protocols, hot baths, and over-dressing are common practices to send heat acclimatization into overdrive. These practices, when done well-supervised and in small doses can be very effective. They do add stress to your training week, so adding these in comes at a cost of recovery.
Portable AC and industrial fan should help a bit, but with overheating trainer all you could possibly do is keep another strong fan pointed at it.
If you live in the southern hemisphere, most of your races in the northern hemisphere winter are in the heat, which is why I usually prefer late evening races.