This may sound a little bit confusing, but I will try to explain. (I have done research on this topic already) I have looked at the temperatures of planets and I was wondering, is there a point where a planet is at perigee and it's temperature cannot reach any higher? Let's just say the planet is tidally locked, and is currently at perigee. Would the planet be at a point where it's temperature can no longer be increased at the current distance from its star?
A planet in a stable orbit can only receive a finite maximum power from it's star and likewise can only generate a finite energy from internal heat (like our cooling core, which is a tiny power output compared to what we get from the Sun). There's a finite limit to available power.
If that power is not radiated out (which is thermal radiation) the planet's temperate would rise without limit. This never happens because hot things radiate heat (as EM radiation) to try and reach thermal equilibrium with their environment (which in the case of a planet is the very cold space around it).
So there must be a finite limit to the temperature any planet in a stable orbit can reach.
As @Cody indicated the actual point of maximum temperature may not be at periapsis.
Atmospheres can act in complex ways to raise the temperature of the surface significantly. Venus is a prime example as this page demonstrates. Without it's pressure cooker-like atmosphere we'd expect a temperature of around 240 K, whereas it's actually a rather staggering 740 K. But all of that is solar powered and can't rise without limit. But it illustrates the importance of atmospheric composition (and indeed the Greenhouse effect) on planets.
Update : I came across another page on the basic theory of planetary temperature while looking into something else. It may be of use so I've added it in this edit.