How weather-resistant is nubuck?

You can get water-proofing spray for them. Do this before you wear them, and re-apply according to directions.

Nubuck is supposed to be more weather resistant that regular suede. Be sure and follow @Prufrock’s advice – spray with a good quality waterproofer like Nikwax. You can get it at larger shoe stores or at camping stores like Dick’s or Cabellas. And, if the boots get wet, after you take them off, do not put them by a heater! This will dry the leather too much.

I wouldn’t use nikwax unless the boots are black as it tends to change the colour slightly.

Nubuck is very water resistant from the point of view of protecting your feet from the elements. However you will find that it changes how looks with age so if you are expecting the boots to look like new for a long time I think you might be disappointed. Some people quite like the way it ages though.