I never quite understand weather changes.
LOL.
Don't worry, those of us who've been playing for years still have problems.
Every army starts the game with 4 PIP-dice including dummy dice.
Correct.
During the game the dummy dice will be removed.
Correct.
The odds that a weather change will take place with 4 dice are much smaller that that it will take place with 3 or even 2 dice.
So during the game the odds that a weather change will take place grow.
Correct.
Is that the intention of the rules?
Good question.
It might be better to consider it a
consequence of the rules rather than an intention of the rules.
I'd call it an
unintended consequence, but others might not want to see things in such a negative way.
I'm quite sure this issue was pointed out in the earliest discussions of the rules back in the late-noughties, but I don't remember what Barker's view was at the time, or what conclusions were reached.
But yes, as the PIP dice disappear in the course of a game, the likelihood of weather changes increases.