Do you need ski goggles to snowboard?

Answer 1

Not necessarily.

You can wear Sunglasses instead of goggles if you want, but you have to wear something to protect your eyes, or you put yourself at risk of Snow Blindness, since light refracts strongly off snow, and damages your eyes.

This is just as true when it's cloudy as when it's sunny.

Wearing Goggles instead of Glasses is however recommended in bad weather, mainly for comfort reasons.

Note: There's no difference between Ski and Snowboard Goggles.