I ride in a climate often where it can be 60 degrees, cloudy and windy and thirty minutes later be in a micro-climate where it is 72 and sunny. Dressing for conditions like that can be a nightmare. Even if you do not live in an area that has a bunch of micro-climates you might climb a long hill, get hot and then on the decent be in a situation where you can get cold from the windchill. The pro cyclists often use newspaper, but given they have gone the way of horse and buggy and that most of us do not have a crowd of crazy fans at the top of the hill cheering us on we need an alternative. I keep a cut open ziplock bag in my back pocket for situations where you get a chill. Just take it out, put it under/between your suspender straps and you’re good to go.