Rain isnt going to hurt your plants unless it rains alot and the humidity is high for a while, like if it rains everyday for a week then your gonna wanna harvest early if it just rains once its not gonna affect your buds because they can dry out. It all just depends on how much rain there is an how mold resistant your plants are. If you see any signs of mold destroy the branch/plant imediatly and you would want to consider harvesting early. you should shake off rain water and morning dew if you are concerned.