What a Cleveland winter actually does to a chimney
No chimney in the country takes a harder beating than one standing over a Lake Erie winter, and the damage is mostly chemical and mechanical at once. Every fire you burn sends acidic, moisture-laden gas up the flue, and a chimney that does not draft cleanly lets that gas cool and condense on the masonry. Lake-effect snow piles onto the crown and works into every hairline crack. Then the temperature swings across freezing again and again, sometimes several times in a single February day, and each cycle expands the water frozen inside the brick and mortar and pries the gap a little wider. The crack that finally leaks in spring was usually opened the previous winter, one freeze at a time.
Creosote is the other half of the problem, and it is the dangerous half. Cleveland homeowners tend to burn long, slow fires through a cold stretch, and a smoldering or poorly drafting fire coats the flue with creosote far faster than a hot, clean burn does. That glazed, tar-like buildup is fuel sitting inside your chimney, and it is what turns an ordinary flue fire into a structural one. A flue fire does not always announce itself either. Plenty of the cracked liners we find in older east-side homes were damaged by a fire the owner never realized had happened. This is why we push for a sweep and a look before the burning season rather than after, while there is still time to clear the buildup and seal the masonry before the cold sets in.