[crasshopper]

In other words "in the 10's" and "in the 20's" are completely unhelpful statements. In Fahrenheit the range you named is 59℉ and 77℉. "Low to mid 60's" and "mid 70's" communicates with fewer significant digits. 50's and 80's tell you something significant with just one digit.

So Belgium is a perfect example of a place where Fahrenheit would be better.

[derobert]

Saying 23 (°C) is less significant figures than "low to mid 70's (°F)" is language lawyering at best. You're ignoring the significant digits expressed by "low to mid".

(And, for the record, "low 20's" °C would be 68–73°F, which is a perfectly useful range, just with a slightly shifted boundary than what both of us are used to.)

[crasshopper]

|{low, medium, high}| < |{0,1,2,3,4,5,6,7,8,9}|

where |s| := the cardinality of s

[derobert]

Well, it'd be "low", "low-to-mid", "mid", "mid-to-high", and "high". So essentially dividing every 2°F, but not really, because the boundaries are fuzzy and quite possibly overlap.

Only slightly less cardinality, a phrase that takes longer to say, and much less precision.