Hi Vikki,
If the dock display isn't following the units you've set, try flipping the units a few times to see if that clears the problem. It might be a problems with the prefs file, sometimes toggling the settings can clear the problem, but if not, it's likely the preferences file is corrupt.
To fix this, quit WeatherCat, then rename your current preferences file (~/Library/Preferences/com.trixology.weathercat.plist where ~ is your home directory) to something like com.trixology.weathercat.plist_old and then launch WeatherCat and set it up again to see if the problem re-occurs.