There are there reasons why our eyes come out of water. First, when our eyes face wind or cold air or some else directly, our eyes will come out of water because eyes must make sure there are nothing in our eyes to stop them works. Second, it can be caused by external injury, trachoma, conjunctivitis, inflammation of nasal cavity and eyelid diseases. Third, it can be caused by atrophy of lacrimal sac muscle. I think your eyes start watering is because your eyes face wind or cold air directly by accident, so it has nothing to do with meditating. It is very common, so you don't need to worry. It is ok. If you still worry, you should go to see a doctor.