20 C - a bit less than room temperature (68 F)
30 C - pretty hot (86 F)
40 C - very hot (104 F)
And going the other way:
10 C - a bit chilly (50 F)
0 C - cold (32 F)
-10 C - real cold (14 F)
-20 C - really really cold (-4 F)
When you hear a temperature in Celsius, don't try to convert it to Fahrenheit, just think in Celsius. 15 degrees is halfway between "chilly" 10 C and "room temp" 20 C. One degree of warming - say 26 C to 27 C - is pretty easy to conceptualize when you have those 10-degree reference points.
If it was always reported to the half point I think we would be able to relate to Celsius better. And if I was making a population wide change I’d ensure reporting was always to the half degree.
Those people are free to use whatever units they like. It doesn't have much bearing on the point that Fahrenheit, which is used in the United States, is a good match for the climate of most of the United States.
OTOH, as far as weather goes, C has the nice property that anything below zero is freezing temperature. In any locale where snow and ice is a thing, that's handy to know.
I'm a scientist and an engineer, and in those applications C is often better. But in daily life, Fahrenheit makes a ton of sense.