Make it Rain

This is a hidden achievement in the game and can be completed once you have entered the Sahara Laboratory.

Description
Set off the sprinklers in end game

Guide

 * There are a few different hallways where you look above and see the sprinklers in the ceiling. For example, one hallway contains an Armsy that you need to get past in order to continue forward. Simply shoot a Fire Arrow or a Flare at the Armsy or down one of the hallways with the sprinklers in order to set them off and complete this achievement.
 * It is also possible to set off the sprinklers in the hallway or some of the offices by lighting weapons with a cloth attached to them on fire.