That's really interesting and something I will have to remember. My friend is from the UK so when we talk about temps (they don't get the winter we get in my area of the US) I try to convert it.

I've been counting along increments of 1.5 in whichever direction from 0 C or 32 F.

I probably made it a .5 for mental calculating.

Just out of curiosity I tried yours and it even works with minus temperatures, although a bit confusing at first.

Yours are exactly the reason I read the comments on posts.

edit: to make it a bit clearer