Whether you can leave your outdoor furniture outside all year depends heavily on the material, your local climate, and the level of protection you provide. For most regions, it's generally not ideal to leave furniture completely exposed to all four seasons without any precautions.
Prolonged exposure to sun, rain, snow, and freezing temperatures can cause significant damage. UV rays can fade and weaken fabrics and plastics. Moisture leads to rust on metal, warping in wood, and mildew on cushions. Freeze-thaw cycles can crack materials.
Some materials fare better than others. Powder-coated aluminum, synthetic wicker (HDPE), and certain plastics like polypropylene are more resilient. Teak and other hardwoods can withstand elements but will weather to a gray patina. Wrought iron is durable but can rust if the finish is compromised. Avoid leaving untreated steel, cheap softwoods, or standard cushions outside.
To minimize damage, consider these steps: Use high-quality, waterproof covers that allow for airflow. Store cushions indoors or in a dry shed during off-seasons. For harsh winters, ideally store all furniture in a garage or covered area. Clean furniture regularly to prevent dirt and debris from causing stains or abrasions.
In conclusion, while you can leave sturdy, weather-resistant furniture outside with proper covers and maintenance, taking the time to store or fully protect it during extreme seasons will greatly extend its lifespan and appearance.