I’m familiar with IAS, (CAS,EAS) TAS and GS concepts but not being used with transonic speed such I never considered temp factor.
I just read it’s really relevat. Form 20 degree to -50 you get as much frontal resistance with a difference of 20% speed (talking about transonic speed)
Basically temperature and air density plays conflicting roles. You get higher to have less air density and diminish your drag but then you get lower temperature that stops you due to sound speed approaching. Interesting topic really.