The weather algorithm isn’t done yet, still has some balance issues and the wind is finicky if you don’t just blow one direction. Still, we’ve put together a simulation for my probability class, so here’s a short video showing how a mage casting a spell in a cell can cause rain to happen. The wind here is moving pretty quickly and so the spell-induced rain moves down wind completely within maybe an hour.If we put it in context and say the mage is moving transverse to the wind going North and wants to use the rain to cover his tracks, then casting the spell just before dawn is a good idea, it maximizes the amount of rain dumped on his location before being blown away. However, if he is traveling either with or against the wind, he could have covered his tracks more thoroughly if had cast the spell well before dawn.
If you’re interested in the underlying math, this document has some errors and is a bit outdated, but gives the gist of the algorithm: MWWeatherAlgorithm.pdf