As a premium user, you can decide which extreme weather you want to receive alerts for, and determine which warning level you want to be notified at. This can be specified either for each individual site, or applied to all the favorites. Just select a location and tap on the icon in the upper right to open the push settings.
Now you can define the alert level from which you wish to be warned, or disable notifications in general - even for single warning elements. To find the definition of each warning colour, go to the settings of AlertsPro and click "Alert Colours".