Ask Tom Why

Dear Tom,
What causes our eyes to water when it is very cold? Wind seems to make it even worse.
— Brian Sapp
Dear Brian,
Tears act as a lubricant for the eyes, protecting the surface from irritants like dust and grit. Tears are produced by glands at the inside corner of each eye, and blinking spreads them across the eyeball.
However, the tear glands step up production when the cornea becomes too dry, and that's the No. 1 cause of tearing.
Very cold air is usually excessively dry, and the thin layer of fluid covering the eye evaporates more quickly.
Wind exacerbates the situation because it constantly blows a new supply of cold, dry air across the eyeball.
Blinking more frequently helps, and wearing protective glasses or goggles will usually remedy excessive tearing.