Some possible causes of E931 precipitation include:
: E931 is not currently a standard, active E number (the 900 series typically covers glazing agents, gases, and sweeteners). However, it is closely related to E227 (Calcium hydrogen sulfite) , a preservative used in winemaking and vegetable processing.
The question is not whether you will experience e931 precipitation probable. It is: Will you carry an umbrella—or stand in the rain with your eyes wide open?
, which describes the statistical likelihood of measurable rainfall in a specific area. National Weather Service (.gov)