Weatherlore

Weatherlore is a skill that, when used, gives you a general idea of the weather conditions and climate, as well as a guess as to the chances of whether or not it will rain. This is useful for preparing your clothing for hot or cold climates. To use it, press Alt+w (v315).

This is not a skill that can be improved by increased usage, unfortunetly. Generally it's not seen as being very useful, although using it once happens to take exactly the right time for some meat/fish to cook.