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.











If I’m not mistaken, he also calculated pi by hand (to several decimal places) during lockdown. So it wasn’t all sunshine and rainbows for ol’ Isaac.