As long as your dog is on a leash to protect it from traffic and you are diligent in making sure no aggressive dogs are present, a safe trip to the beach and park can be made after 4 months (16 weeks) of age for most puppies. Puppies have a variable maturation of their immune systems. They get antibodies to common viruses—distemper, parvovirus and hepatitis—from their mother, but the timing for when the mother-granted antibodies stop working and the self-made antibodies start working is different for each individual puppy. That is why puppies need a series of shots. This is the reason that Rabies is not given until 16 weeks when the immune system is able to recognize proteins and make antibodies to them. Always check with your personal veterinarian regarding your particular puppy’s antibodies and immune system readiness.