I know when there's likely to be snow or ice on the ground by the advanced and admittedly sometimes hazardous techniques of looking, and in some cases actually

I know when there's likely to be snow or ice on the ground by the advanced and admittedly sometimes hazardous techniques of looking, and in some cases actually also going, outside. I know how to tell when water is boiling or frozen, likewise, by the primary evidence of sense impressions. What were you saying about humans needing a number on some specific scale for that?