The answer depends heavily on the specific materials and construction. True all-weather modern urban furniture, made from powder-coated aluminum, stainless steel, teak, or high-quality synthetic rattan, is designed to withstand sun, rain, and snow. These materials resist rust, rot, and UV damage. However, "all-weather" does not mean "maintenance-free." To ensure longevity, regular cleaning and the use of protective covers during harsh winter months or prolonged storms are highly recommended.
For furniture with cushions, the frame may be weather-resistant, but cushions are not. They should be stored indoors or in a dry place when not in use, as constant moisture leads to mold and mildew. Furniture made from untreated steel, iron, or certain woods will likely rust, crack, or degrade if left exposed year-round.
Ultimately, check the manufacturer's specifications for "all-weather" or "year-round use" ratings. Even with durable furniture, proper care and occasional seasonal storage for sensitive components will significantly extend its life and keep your urban outdoor space looking pristine.