Yes—but not automatically. Urban planter boxes can stay outside all winter without cracking only when the container is frost-resistant, has excellent drainage, and is managed so water cannot collect and freeze inside the soil or between the pot wall and root ball. Cold alone rarely breaks a good planter; repeated freeze-thaw cycles are the real problem. When wet soil expands as it freezes, it can push outward on the walls. If the box is thin, rigid, sealed, or already stressed, that pressure may lead to hairline cracks, spalling, or split seams.
Material matters. Rotomolded resin, frost-rated plastic, high-quality fiberglass, and well-built wood planters are usually the safest choices for an exposed urban balcony, roof terrace, or sidewalk. Thin terracotta, glazed ceramic, concrete with hairline flaws, and cheap brittle plastic are much more likely to crack, especially if they are planted and left full of wet soil. Metal boxes do not usually crack like ceramic, but seams and finishes can fail.
Winter care makes a big difference. Confirm that every planter has open drainage holes and empty any saucer or tray that can hold water. Raise the box slightly off cold pavement so water can escape and the base does not sit in ice. Avoid overwatering in late autumn; keep soil lightly moist, not soggy. Add a layer of mulch to reduce rapid temperature swings, and shield exposed boxes from strong wind if possible. Do not walk on or bang frozen containers, because cold materials are more brittle.
If you live in a severe-winter area or own a fragile ceramic or terracotta box, the safest option is to move it to a sheltered position, empty it, or store it indoors. For durable resin, fiberglass, or wood boxes, leaving them outside is usually fine with drainage and sensible winter care. So the answer is yes for suitable, well-drained urban planter boxes—but fragile containers should not be left exposed all winter if you want to avoid cracking.