How to make an attack that triggers a weather event in battle to last x turns?

[McMillan]

So, there's an attack I have in mind where swords fall from the sky for 3 turns. However, after the character uses this sword skill, he can freely use other skills or moves while this effect is in place. This isn't Jump from FF, or Solarbeam from pokemon, or an attack that the character repeats for 3 turns. It's more like Sandstorm/Sunny Day from Pokemon.


How can this be done?


EDIT: I also want this weather effect to take place at the end of a turn.

 

[Andar]

Have the skill set a variable to 3 (for the number of turns) and have a troop event run at the end of each turn checking that variable - if it is greater than zero, one turn sword rain and then count the variable down.