During the winter, a chimney faces prolonged exposure to wind-driven rains and melting snow. Being exposed to this weather can lead to chimney deterioration, a potential safety hazard for occupants.
Luckily, General Shale has a checklist ready for you to make sure your chimney is ready for winter weather including everything from the chimney walls to the cap:
For maximum weather resistance, a chimney cap should extend beyond the chimney walls and incorporate a drip feature at its edge. This prevents water (from melting ice or snow and straight-down rain showers) from streaming down over the chimney walls for long periods.