Your geo targeting is always set in AdWords (campaign level) or Facebook (ad set level).
If you are targeting large areas such as countries or states, WeatherAds will break up your geo targeting into more granular constituent parts, which then enables the platform to play/ pause ads or modify your bids based on the weather in each location. This does not affect your overall campaign settings, because WeatherAds works within the boundaries of your geo targeting zone(s).
Example: if you were to target the state of California, WeatherAds will break this down into LA, San Francisco, San Diego, etc in order to accurately apply your weather targeting rules to each city based on the local weather in that location.
Further reading: What types of geo targeting does WeatherAds work with?