majority of the time, higher pressured tires will keep lower temperatures.. actually.. thats true for all the time; HOWEVER.. if you do get them hot... it will take much longer for them to cool off
think of it as one of the simple law of physics:
less particles = less energy needed to heat up few particles
more particles = more energy needed to heat up lots of particles
however, this works vice versa ; less particles means it takes little time for it to cool off, since it is only a few partcles that are heated
so basically.. like all things, there is a medium that you want to be in, you want them to stay cool.. but you also want them to cool off fast
so when your outside temps get hot, it uses the inside temperature to cool the outside off; a dependant system; when your inside temps get high, its harder to cool off the outside
also keep this in mind; the bigger the difference of the temps, the more drastic reaction will occur, meaning that if the outside temps are in red, and inside is in blue, it will cool off the outside faster, as opposed to having a green outside temp, and a blue inside temp. in basics.. the bigger the difference, the faster something will occur
but this is speaking in physics terms, not actual events