I don't ride my bicycle in -15 °C, but I've found it much harder to exert myself in temperatures from -5 to 5 °C versus 20 to 30 °C. That is, hills that are no

I don't ride my bicycle in -15 °C, but I've found it much harder to exert myself in temperatures from -5 to 5 °C versus 20 to 30 °C. That is, hills that are nomally easy for me in higher temperatures become very difficult in lower temps.