Hop in a car that's been baking in the sun for hours, and you'll wish you'd opted for cloth upholstery instead of the luxurious leather seats that also added $1,200 to the sticker price. If you're wearing shorts, you'll think you suffered second-degree burns. Now there's an alternative: leather that is treated to absorb the sun's rays and stay cooler in summer.

Called Sun Reflective leather, it undergoes a process that embeds a special pigment in the leather during production. The pigment reflects infrared radiation (like the red heat lamps over the French fries in a fast-food restaurant), which causes warming in the spectrum above 720 nanometers. The first application of Sun Reflective leather comes in the 2007 3 Series convertible from BMW, which is slated to be announced at the North American International Auto show January 7 in Detroit, where warm seats would likely be a hit.

Sun Reflective leather can be applied on seats, seat backs, and armrests, and has no affect on the look, feel, or smell of the leather, BMW says. On dark seats made with Sun Reflective leather, surface temperatures will be as much as 68 degrees cooler. There's a noticeable but lesser impact on lighter upholstery, where the solar effect is less severe. The benefits are greatest on surfaces directly in the sun's path, which especially affects convertibles with the tops down. For hardtop cars and convertibles with the top up, the heat buildup on seats is often indirect, as the entire interior gets warmer.

The BMW 328i and 335i convertible are expected to ship in spring 2007. Pricing hasn't been set yet.

To read about BMW's 2007 hydrogen car, click here.