You do realise water can fall from the sky, right? 100°C might not be too useful for outside temperatures, but knowing if there might be ice on the road or not seems like a useful thing to know.

Also, as a maths teacher, having frequent negative temperatures makes working with negative numbers a lot more intuitive for students. The fact that Americans apparently use 1 for the ground floor means I’d lose out on both of my simple real-world examples of negative numbers.