Weather is so unpredictable these days. A person may not see a rain-cloud in the sky and probably say to themselves, “It’s going to be a nice sunny day.” As a result, they leave home unprepared for the rain; they leave their umbrellas and raincoats in their respective areas, because in their minds, they have no need for them.
Then, later on in the day, it rains as though a storm is approaching and they get themselves thoroughly soaked from head to foot.
From experience, I can say to you that I have been drenched in the rain and then had my clothing dried (with me in it), by the Sun that came out after.
I think that when the weather-person is giving a report, the should say that there would be a 65% chance (or whatever percentage they think it is at the time), that we are going to have sunny weather, etcetera. Some of them are even honest enough to let you know that you can look out for a few scattered showers; I prefer this instead of those absolutes that they like to give; for example: they telling their listeners, or viewing audience, that it is going to be a beautiful sunny day (In my opinion, this can cause the weather-person to lose their credibility when the opposite of what they said happens).
In a figurative nutshell, the weather-person is just a human being like you and I. Although those individuals are supposed to be well-trained in their field of work, I wouldn’t recommend that you take their word as the Gospel truth.