Hot Nascar cars

As the temperatures are rising here in Las Vegas, today's RJ had a column about the heat in the new style Nascar vehicles. Dale Jr. was obviously suffering when he climbed out of his car at the end of Sunday's race.  Denny Hamlin and Brian Vickers made comments about the extreme heat. With the design of the cars creating somewhat of a greenhouse effect and the safety changes that may contributed to holding warmth in, will the heat become a safety issue of its own for the drivers? Especially in some of the hotter and more humid race tracks. There is a reason they race here in March and not August.