The simple answer is that while many modern outdoor cushions are designed with weather-resistant materials, it is generally not recommended to leave them outside exposed to heavy or prolonged rain. Most cushions labeled as "all-weather" or "weather-resistant" are made from fabrics that dry quickly and have some level of water repellency. However, they are not fully waterproof. Consistent exposure to rain can lead to several problems. The cushion's foam filling will eventually absorb moisture, leading to mold, mildew, and a musty odor that is difficult to remove. Furthermore, constant wetness can break down the foam, making it lumpy and uncomfortable, and cause the fabric to fade or stain.
For the longest lifespan, the best practice is to store cushions in a dry place when they are not in use, especially during extended periods of rain or the off-season. If daily storage is impractical, investing in high-quality, waterproof storage bags or a dedicated outdoor storage box is an excellent alternative. For frequent use, consider placing your furniture under a covered patio or using a waterproof furniture cover. Ultimately, while short, light showers may not cause immediate harm, proactive protection is the key to maintaining the beauty and comfort of your outdoor cushions for years to come.