The simple answer is: it depends entirely on the cushion's material and construction. For long-lasting beauty and comfort, bringing cushions indoors during rain is generally the safest practice. Most standard fabric cushions are not designed for prolonged wet exposure. Water can lead to mold, mildew, fading, and damage to the cushion's filling.
However, many modern "all-weather" or "weather-resistant" cushions are made from solution-dyed acrylics, polyester, or other quick-drying, UV-stable fabrics. These can withstand occasional rain, but they will still last longer if kept dry. The key is to allow them to dry thoroughly after getting wet; trapped moisture is the main enemy.
For true urban outdoor convenience, consider these solutions: invest in high-quality all-weather cushions, use a dedicated waterproof storage bench, or opt for furniture with built-in storage. A protective cover for your entire furniture set can also offer an extra layer of defense. Ultimately, a little care—storing cushions during extended rain or harsh weather—will significantly extend their life and keep your outdoor space looking fresh.