Chronic conjunctivitis, dry eyes and Snow blindness can all cause watery eyes. Some people have watery eyes because their tear ducts massaging is blocked. If you have snow blindness, bright sunlight reflected from snow would burn your cornea. You are sensitive to lights and would keep tearing.
A blocked tear duct is the most common cause for watery eyes. My mother has trachoma and she also has watery eyes especially on windy days. Other disease like dry eyes, Ectropion, Entropion may also cause watery eyes.
Watery eyes may be caused by some eye diseases, such as Niphablepsia, chronic conjunctivitis, obstruction of the nasolacrimal duct, Blepharitis and dry eye. Therefore if you get watery eyes, you'd better go to see an doctor to find out the reason. Then your watery eyes can be treatedly specifically.