That's a great question, and you're definitely not alone in dealing with this frustrating issue. It's a common problem that comes down to the fundamental properties of the plastic used in most standard outdoor bins.
The main culprit is the cold temperature itself. Most residential trash cans are made from polyethylene or similar plastics. These materials become progressively less flexible and more brittle as the temperature drops. Think of it like a rubber band—at room temperature, it's stretchy and resilient, but if you freeze it, it becomes stiff and can snap easily. The plastic in your bin undergoes a similar, though less extreme, change.
When the plastic gets cold and brittle, it loses its ability to absorb impact and flex. Normal use—like rolling the bin to the curb, a gust of wind knocking it over, or even the pressure from packed-in trash—can create small stress points. In warm weather, the plastic might just bend or dent. In freezing conditions, those same forces cause the rigid material to crack or split.
There are a few other factors that team up with the cold to cause the damage. First, UV degradation from summer sun weakens the plastic's polymer chains over time, making it more susceptible to failure later. Second, the plastic itself undergoes thermal contraction; it literally shrinks a tiny amount in the cold, which can pull on already-stressed areas. Finally, if there's any moisture inside a crack or seam, it can freeze and expand, forcing the crack to widen significantly.
To prevent this, consider storing your bin in a garage or shed if possible during the deepest cold. If you must leave it outside, try to place it in a spot sheltered from strong winds. When buying a new can, look for ones labeled as "all-weather," "heavy-duty," or "frost-resistant," as they are often made with compounds designed to remain more flexible in low temperatures. Also, avoid putting boiling liquids or very hot ashes into the bin in winter, as the extreme temperature shock can be particularly damaging to cold plastic.
In short, winter cracking is a battle between rigid, cold plastic and the physical demands placed on your trash can. Upgrading your bin or giving it a bit of shelter during cold snaps are the best ways to win that battle and extend its life.