This is how I use this skill. So far, I’ve only played one-season-per-session, so that may be affecting things.
When the mice set out at the beginning at the GM’s Turn, I ask them to make a Weather Watcher test. If the fail, I hit them with a planned weather-based complication after a later, failed Mission Obstacle test. If they pass, they basically have a “Get Out of Weather Free” card if I want to use a weather-based complication.
Earlier today, I decided I didn’t like this. My new thought is to ask for the Weather Watcher check in response to the failed Obstacle test that would bring the bad weather, as in “You failed your Pathfinder role. You’re going to get stuck out in the freezing rain unless you make an Ob 6 Weather Watcher test,” rather than have them make Health rolls to avoid getting Sick or whatever. If they fail the Weather Watcher roll, I can hit them with conditions anyway.
This seems to sync-up better with the Mouse Guard mechanics, but at the moment I’m thinking Weather Watcher might simply work better in longer campaigns.