The answer depends heavily on the material. Traditional natural wicker (made from rattan, cane, or bamboo) is not designed for prolonged exposure. Moisture can cause it to warp, crack, and mold, and UV rays will fade and weaken the fibers. For natural wicker, seasonal storage or use in a completely covered, dry patio is essential.
However, modern synthetic wicker (often made from resin or polyethylene) is typically built for all-weather use. High-quality synthetic wicker is UV-resistant and waterproof, allowing it to withstand sun, rain, and snow. Even so, for maximum longevity, it's wise to take some protective measures. Using fitted furniture covers during harsh winter months or prolonged periods of non-use is highly recommended. This shields the furniture from extreme moisture, dirt, and UV degradation, preserving its color and integrity.
Regardless of type, placing wicker furniture under a pergola, awning, or deep eaves offers significant protection. For ultimate peace of mind and to extend your furniture's life for many seasons, storing cushions indoors and covering or moving the furniture to a sheltered location during the worst weather is the best practice. Always check the manufacturer's care instructions for specific guidance on your set.