The best way to prevent the saddle from getting wet is to get a water-resistant one. You'll see that the water drops will slide off from the saddle when it falls on it. If you are worried about the rain, you can simply use a raincoat to protect your saddle from water. If your saddle gets wet by any chance, you don't need to get worried either. Try to get as much water out of it by squeezing it ever so gently. Then, you can just place it under sunlight, and after a few minutes, the water will go away completely.