Normally, this is not so much of an problem in open cockpit cars (like F1), but it´s a problem in closed cockpit cars (Touring Cars, Rally cars, GT etc.).
And in these racing series, driver use such suits, the technology is there.
But it is a tad heavy, so you don´t use it, when you don´t need to.
looks something like this:
http://www.coolshirt.net/