They can’t predict the weather because it’s mathematically impossible to predict the weather. Weather is a chaotic dynamical system which is 100% deterministic, that means that there is no probability model for weather. Thus all weather predictions are wags (wild a$$ guesses).
But they can affirm, with 100% certainty, that 100 years from today we’ll all be living in grass shacks and sipping on pina coladas on the coast of Greenland if we don’t do something drastic like get rid of all our cars....................