Generally speaking, it takes at least an hour for fans to soak in cold water. The water temperature is too low in winter, so it takes a long time.
But there is a simple way, which is to heat the water first and soak the vermicelli in hot water. The vermicelli becomes soft quickly and can be soaked in ten minutes.
The softness of vermicelli is also related to the purity of vermicelli. The higher the purity of vermicelli, the less impurities, the easier it is to soak vermicelli than vermicelli with impurities, and the better the taste.