I don't think anyone mentioned that colder air is more dense. Also, we tend to limit our output when we know it will cause a heavy sweat inside our insulation.

Still ... I suspect that the malleability of the tires and viscosity of the grease in the components play a much bigger factor. Race car drivers will talk about the temperature of there tires affecting handling. This is the reason they swerve their cars under caution. I would suspect that tires have a "sweet spot" temperature wise with minimal rolling resistance. Above which ... they start coming apart.