what should the normal operating temp for the heater on a 2006 ford explorer.

I have the vent on and the heat full blast. It is blowing around 152 in the front and if i turn the back on it is about 180

Sounds like it's heating well.Are you experiencing a problem?

What would make the back heat 30 degrees hotter than the front

Different air volume and core temp. (separate heater core for the back-you are aware , right?) How close to the rear heater core are you measuring the temp. , compared to the front? the front is split more and traveling further through the dash (just a theory , I don't know the exact layout for it)