Originally Posted by TurbineBlade

Why, because you'll be riding across Greenland for days without a place to take shelter? Seriously, cotton works fine. I actually prefer it. I ride year 'round in it -- here in DC it was about a 17F (morning in January) to 104F temp range in 2009 from extreme to extreme. Yeah, if you get it sweaty-as-heck it draws heat from the body (which makes it great in the summer BTW), but if you just use light layers and are willing to START OUT COLD you'll never build any sweat and you'll have nothing to "wick" away.

Plus it's cheap and doesn't smell like crap during use (like most synthetics do). Plus you probably have dozens of t-shirts already.

Or go into your LBS and buy a lot of name-brand, overpriced plastic, sold by well-meaning people who likely don't ride 4 months of the year. Just stay away from open flames and woody vegetation.