For my adventure I am placing it near a volcano that exploded in the fall. The ash cloud made the snow into ashy mud and will make the winter last longer leading to a crop failure in the following year. The volcano was in a mountain range masked from view by the surrounding farmerlings who don't know why the summer won't come. 

Cloudlings are avoiding the area since the particulates are causing problems with their engines.  Before the eruption they didn't travel close to the mountains because of flying megafauna that roosted in them and the untouched wilds that the farmerlings avoid, so they didn't see the volcano.

Since there is little or no explanation as to why the winter is lasting longer, people will reach out to to grasp any explanation no matter how outlandish leading to manias and scapegoating.

Ooh, I like the idea a lot! Are you thinking of creating more of a sandbox location, or an adventure? Looking forward to checking it out either way!

I have a specific problem for the players to solve. But I think this would be a great setting for all sorts of problems to crop up and have players solve. Desperation and fear of from the unknown and unknowable is a great inciting incident.

It would make parts of The Spread more hazardous with pockets of toxic gas, more particulate ash, and added lighting. An adventure could involve rescuing a downed cloudling ship, or having a Farmerling Village have to host surivors beyond what their food stores allow.