If you are looking for dependable weather then April on Cape Cod is not for you. With that said, the sun is warm, the flowers are out and if it storms...it usually does not last long. Definately no snow in April that will be a problem. Cape Codders dress in layers because it could be 70 or 40 degrees. Your best bet is to stay in a place that will give you shelter and comfort if it does urn cold or stormy. There is nothing like taking a brisk walk along Coast Guard Beach in the National Seashore, sunning in the shelter of sand dune, then returning "home" to curl up next to the fire with a good book and glass of wine.... Or spending a day browsing the shops in Provincetown or Chatham, Having a steamy bowl of chowder for lunch, catching a glimpse of the fishing fleet returning with the day's catch, biking through the dunes or along the bike path, or kayaking in Nauset Marsh. You can do all of this in April without worrying about the traffic or crowds! I say go for it!