Sort of like the weather outside. Rain rain go away...
The WSG index has:
collecting - maths formula for volume in a cylinder, melted snow to water ratio is 10:1,
determination - coming soon W is for weather
effects on combat - will make the effects for gusts and gales worse
extraordinary - rain that goes on and on
extreme - Hail, Sleet, Lightning, Snow (interesting just descriptions and timings for how long the precipitation will last - not really linked to mechanical effects)
portable shelters - covered in C is Camping and Comforts, with the moisture resistance for certain types of tents and shelters.
(quick post today)