leather no matter what color (mine are alpaca and anthracite) is hot in the summer. no way around it. the only option other than cloth seats would be a set of alcantra seats from a srt-6.
what i do with mine is i bought 2 huge beach towels. toss em in the trunk. when you park with the top down toss the towels over the seats and it helps. other than that its a trade off for having beautiful seats