Both of us coughing only in evening and morning?

My 20month old daughter and I both develop a 'productive' cough in the evening and wake up with one at morning time. We also experience a runny/stuffy nose. But during the day all of this is seemingly nonexistent. I live in south texas where allergies breed. What can I do at home to get some relief? (I try to keep my remedies as homeopathic as possible.) Should I run the A/C, open a window, turn the fans off? I think I read a humidifier may help?