While doing anything… 70F is pretty much perfect temp for most people. You’ll cool down fairly quickly after any heavy activity and will be safe during said activity unless you’re in direct sun, not drinking, and not taking breaks, but all that is true in nearly any temp.
70F is roughly 20C
I don’t see the connection… the 24 hr Le Mans race is completed by multiple drivers switching out every few hours so no one is driving 24 hours straight. That’s not how endurance racing works