I have had this also, sounds exactly like what I have been going through...sometimes caughing makes the mucus worse for me, or hot or cold air. I have mild asthma and when the excess mucus comes I use my rescue inhaler, which sometimes takes about 5 minutes to work. Its very scary when it happens and it sometimes seems to come out of nowhere, although I do think it is some sort of an allergic responce as it has happened to me while doing yard work in the heat. It also seems to be aggravated by fresh cut grass. I am taking prednisone 10 mg and soon to be taking Flovent and singulair to see if this has any effect on my symptoms. It is very strange though because I done very well on all of my Asthma tests that I had over the summer, I wonder if it is some sort of allergic reaction that is triggering this, or if this is asthma?