Making sure your HVAC system is functioning year round is important, especially in times where weather changes and patterns that could occur are mostly irregular. Keeping your family adequately cool in the summer and warm in winter is the most certian and foreseeable luxury you can give to them. The causes of an air conditioner or heating systems breaking down in winter are debris of ice, frost or settling night time dirt which could clog up condenser coils or the debris could constrict affect airflow. Its important to have a qaulified HVAC company to check all compenents, lining and parts needed for servicing periodically.