Fireworks along with the snow effect are offered daily, weather and wind permitting.
Disney does have to cancel them on multiple days, but won't know until right before the planned show, or even a few minutes after the scheduled start time.
Wind at higher levels is a big one that cancels the Fireworks.
The Snow effect is often offered as a stand-alone instead. The issue with the Snow is that in reality it is soap (glycerin) bubbles, so if it is raining, they won't offer them, since it would make the walkways slippery.
So it is on the daily schedule, but no guarantee that they will be offered.
Parades can change daily, and rain does effect them, sometimes causing cancellation for safety reasons. They do have a small rain day Cavalcade that they use as a substitute.