yeh, if you had a digital temp gauge (i use my pfc hand controller) you would see
if your not driving and having air blowing through your cooler etc your car actually heats up at idle
not much but for example
my car usually operates at around 80-82 degrees
i sat in the car park and ate maccas with the air con on one hot day and the temp got up to 105 degrees and went back down after i started driving again
the day and air con did play a part so the temp rise isnt usually as big
best to turn it off..