While I doubt anyone's surprised by the existence of Just Cause 4 at this point, given that two leaks have happened in the last week, we did just learn its release date during the Microsoft conference: 4th of December. In the footage, we see a few instances of exciting weather: first a tornado in the distance, and later a plane being pulled into one.
It otherwise looks like Just Cause as we know it: open world excitement, the wingsuit from Just Cause 3, lots of vehicle types and more.
There's also a dev diary below. It explains that there are four biomes in the game. Rico is up against The Black Hand, a private military force. The game's got an all-new engine, too, to support more elaborate weather physics and more. Expect sandstorms, blizzards and thunderstorms.