The most common cause of watery eyes is chronic irritation of the eyes, typically from exposure to irritating substances in the air (such as dust particles) or from eye allergies, for which the medical term is allergic conjunctivitis. The chronic irritation to the surface of the eyes caused by these conditions stimulates tear production as a defense mechanism, which leads to the watery eyes.
Other symptoms that are associated with chronic irritation of the eyes would include eye redness and eye itching. If you have these symptoms, you should definitely see your primary care doctor
as soon as possible, as there are very effective medications that can be used to treat these symptoms, including oral anti histamine medications (like loratidine/Claritin and cetirizine/Zyrtec) as well as various types of anti allergy eye drops.
Another, much rarer, cause of excessive tearing is obstruction or partial blockage of the tear duct that is supposed to drain the tears away from the corner of the eye into the nasal passages. When you go to see your primary care doctor, in addition to evaluating you for chronic eye irritation as the cause of your excessive tearing, they will also be able to assess if you might have any duct blockage.