Hi Azhar,   Chronic coughing that is worse during the night is definitely a common symptom of asthma. And in kids, it is often the only symptom. But you should bring your son to his doctor to be sure. Only a doctor can diagnose asthma for sure, using a combination of medical history, examination, and testing.   If it is asthma and only occurs during the winter, it could be related to seasonal allergies, which are set off by certain factors in the environment. In your son's case, these triggers could be indoor allergens (because he's inside most of the time during winter) or other allergens that are more common during colder months.   Regardless, it's important to get your son evaluated now, and started on treatment, if necessary.   Take care, Kathi