When I was working on a teaching certificate some 20 years ago I took a weather class. One of our assignments was to plot the weather prediction 5 days out, then 4 days out, until day OF (same source.)
I have thought about this many times. I have concluded that 5 days out is generally correct OR it is Way off.
If you learn to read the clouds you can guarantee that "mare's tails", Then those clouds that look like cotton pulled apart, altocumulus clouds--all over the skies means a guaranteed storm some 24 hours later.
There are Many factors that go into forecasts, including fronts, winds aloft in the stratosphere, where the ice clouds live, Cirrus, that interplay. Depending upon which winds, cold fronts and warm fronts are the most powerful, Those will prevail.
ALSO, the Jet Stream often gets stuck in a wet period or dry period, and it takes a very strong system to break this up, hence long periods of drought.
Just so you know there IS some science involved, and, just like in the law, it depends upon the interpreter.