The Rain Tiger at Will Technique is a contact-type perception ninjutsu, allowing one to freely manipulate rain infused with the user's own chakra.
The rain falls from rain clouds, formed with Pain's own chakra. During this technique, the falling raindrops are closely linked to Pain's senses. When the rain is obstructed by a chakra belonging to someone not of the village, the existence of the intruder can be detected. The detection of the rain however is not specific as Pain can only know if someone has entered the vicinity of the rain but not where specifically they are. Upon knowing an intruder has entered the rain's vicinity, he needs someone who specialises in covering large areas to find the intruder's specific location. The rain will keep on falling until Pain uses the seal to cancel it. Pain made it rain every Sunday in Amegakure, or whenever he had to leave the village.
The tiger is well-known for its ferocity and watchfulness. It keeps a very close guard on its cubs, watches vigilantly for an opportunity to catch its prey, and walks great distances to patrol its territory; all a reference to how Pain uses this technique to vigilantly watch over the village.