Crusader Kings II

Pretty simple, just play as a West African pagan king or emperor (I did Ghana 1066 start), put on max speed, and wait for events about threatening droughts in one or more of your provinces. Always pick the perform rain dance option (it'll cost ~90 gold) and wait and eventually you'll get an event for one of them where the rains start again giving you the achievement. It took about 15 or so years to fire for me.