Thanks for the ideas folks, the party is already on an adventure to retrieve a mcguffin so I’m not interested in starting a whole new threat, just trying to throw some obstacles in their path so that the journey is memorable and challenging. The storm is not intended to be the entire adventuring day but a reason to seek shelter in an ancient temple that provides its own set of challenges.
I like the multi-planar storm and perhaps that’s a hook for some follow on adventure? But the players are at level 20, so I’m looking to wrap things up with this final adventure