Hi . I found it was the IV chemos like oxaliplatin that caused the cold air problems not the capecitabine? If you are really worried though then just wrap a scarf around your lower face or wear a close fitting face mask. I always wore gloves (despite not liking them!) as my fingers would get tingly and also a longish coat as my thighs seemed to feel the cold.
Enjoy your walk - I love all the lovely colours at thus time of year
