this is the best weather mod I know of it adds wind that if it is strong enough can move you! Tornadoes that really move the blocks and mobs including you!
in order to make any changes to the "rules" of the weather go to %appdata% enter roaming goto .minecraft
find config and click mod_weather and modify as you please!
tornado mod for 1.2.5 http://www.minecraftdl.com/weather-and-tornadoes-mod/
my zombiecraft world http://www.mediafire.com/?7jkz66ktyrljjr8
have fun devastating minecraft!!!!