I'm another asthmatic. I find the various responses to conditions and to exercise interesting. For me, I'm better off in summer but still limited in that I run out of air during a strenuous effort. In winter I'm much more limited in how big an effort can be produced but as long as I stay below my threshold I'm able to ride with as much enjoyment as summer. I do regret not being able to sustain a fast effort. It seems that the bike wakes up and really begins to perform at 20 mph or so. I guess I should be glad these efforts don't put me down so that I find little kids circling like buzzards.