Again, Im not saying anything definitely and the general consensus is and probably should be he is performing very good in the cold whether. Perdon me for not remembering, but I am pretty sure I read somewhere that he prefers good weather. Well, probably everyone does bar a few, but also performs better (in relative terms). Coupled with the times he has picked up colds, 2014 Giro, 2015 Vuelta (if I remember correctly, wasn't there a sudden change of weather after the very hot week, I'm not sure) and post Catalunya, I think Quintana is one of the more fragile riders in terms of getting sick and adjusting to cold, maybe also heat in terms of not performing as well when it comes to heat. I could be completely wrong, but thats just a few things I have picked up. Bottomline, he seems to pick a cold or some other sickness up more than most.
Again, I know we have a few Columbians on this site who probably follow Quintana more than I and thus are more educated. I am perfectly aware of Quintana has had some brilliant performances in cold, my mistake for bad wording, I didn't mean to say he was performing under par in cold conditions, rather that his health is more fragile than most