I've not had this problem before. What type of stain are you using? Did you let the stain dry completely before you sealed it? I sometimes have trouble if I don't, but am not sure about this problem. I guess it could be the humidity--I wouln't know. I live in Lubbock where we don't get much rain. I doubt that retarder would help. I've never heard of using it for stain.I often use it for lacquer though. (It does rain occasionally)