I dunno about that - been metric all my life and I know the difference between 23 and 28 degrees C. Since it's something you generally grow up learning about, the practical usability (by lay users) in terms of dealing with estimating temperatures is something that is picked up along the way too.

Additionally, weather reports will usually qualify the temperatures (with things like "warm and sunny" or "hot" or whatever), which is needed regardless of measurement - 25 degrees C in humid conditions is a very different "feel" from 25 degrees C in dry conditions. Add in wind chill/warm factors and temperature by itself is not actually that useful by itself to determine the weather practically.