in the original the (anti magic/sparkle) weather changed more rapidly.
See the attached savegame of the original. You are in the cube generator, you see the sparkle rain, double click on the cube. You will be teleported outside and the rain will end in about ten seconds.
In Exult it takes much too long to change, when moving between chunks. This might be wrong for the anti magic rain. Savegame for Exult also attached.
Diff:
Should be working on latest SVN.
continued in https://github.com/exult/exult/issues/155