Genuine leather seating surfaces will have invisible natural pores in it (since it came from animal skin) to allow it to cool down within a reasonable time. Leather apparently works well enough in the Middle East and in the hottest parts of the U.S. so I guess it'll work for us too.

Some very high end vehicle have heated and cooled seats (e.g. Saab, Mercedes). Leather is also initially uncomfortably cold during wintertime.

I used to have cloth seats but now I'm on leather. The leather cools fast enough before I have time to complain. Or is it because of the good a/c? :D