Your exhalation may be getting into the inside of your goggles. Were they on tightly?

Also, goggles usually come with a lens defogging cloth. If you don’t have one, you can get one in the lodge store for a couple dollars. You need to wipe the inside of the goggles in the morning.

@zenvelo is probably correct. Make sure you have them adjusted correctly and a good seal in place.

Do you have facial hair? Serious question. If you do it will keep them from sealing correctly. It has nothing to do with either the snowboard or that it was your first time.

I also find they will fog up in the morning until they (and me) adjust to the outside temp.

I can’t tell you exactly why, but this is a common problem. Ski shops sell a liquid (or a defogging cloth) that you can apply to the inside of the goggles to prevent moisture inside the goggles.

Can you spit in them and wipe it out like you do in swim goggles?