Prolonged coughing with seasonal recurrence is the result of multiple factors which are high during the particular season. High amount of pollen exposure may have induced a hypersensitivity in your immune system. A viral infection common in spring and summer can trigger a respiratory inflammation which due to the hypersensitive immune system becomes exaggerated both in severity and duration. A common after effect of such viral infection is allergic rhinitis causing post nasal drainage which is the commonest cause of cough lasting more than two weeks.

Acute bronchitis is caused by viruses and, rarely, bacteria; chronic bronchitis is primarily caused by tobacco smoke.