Barring Control Weather or other unnaturally weather alteration, how reliable is the weather prediction part of Druidcraft cantrip?
You create a tiny, harmless sensory effect that predicts what the weather will be at your location for the next 24 hours. The effect might manifest as a golden orb for clear skies, a cloud for rain, falling snowflakes for snow, and so on. This effect persists for 1 round.
Someone mentioned that this can be used to predict cloudy night to prepare sneaking into the castle. But can the prediction fail without magical interference?