A Natural Disasters expansion was just announced for Cities: Skylines that will add in a number of natural disasters (obviously) in addition to an in-game radio, alert systems for cities, and new hats for Chirper.
Natural Disasters will include:Deep, Impactful Gameplay:With Great Power Comes Great Response Abilities:Radio Saved the Video Game:An Objectively Good Feature:Chirpocalypse Now: Heck yeah, new hats for Chirper

This expansion is slated for a Winter release for the Windows, Mac, and Linux versions of the game.