Just a cautious addition/change to the above steps.
After you Quit WeatherCat in
step 1, drag the app to your Desktop or any other location (except the Trash)
outside it's current location/folder. This way, you will
still have the working app in the
very rare change that the new app is somehow corrupt (from the download?). This will also allow you to skip step 2
and 3, as there will be no conflict to warn about.
The point is, the WC app does not store your data in itself. All that data is in various files in your user/Library and the app's plist files. That's why it is safe/normal to simply replace the app with the new version. I simply use this procedure for any important app I update. Actually, I compress the old version and keep it until I have proven, to myself, that the new one is purrfect! With WC, this is being overly cautious, you've probably seen the very large number (198?) of updates/testing with the app's development. Still, as they say, "If you don't plan, you plan to fail!".