When I travel outside the US and have to discuss temperatures with people, or I'm talking to foreigners in the US, I convert to C in my head and use that.

It probably isn't that hard for you to just convert in your head.

There's never a need to use anything else than Celsius, in Europe. Ok, we do learn Kelvin in school but you wouldn't really use it in a normal conversation.

There's never a need to use anything else than Fahrenheit the US either, but I still learned how to use Celsius.

No, it's not, because it's not just a multiplication but also an addition. If I would live in the US for some time maybe I would develop a knack for it, but for now it's too much effort for something that only a few places use.

I don't use multiplication or division. I just know 0=32, 10=50, 20=68, 22=72(aka room temp), 30=86, and 40=104 (aka really hot). I just estimate from there.

As a continental climate dweller I also know 0f = -18c, -20f = -30c, -40f = -40c.

Your loss, it's pretty neat

What's his loss, exactly?

Not having experienced the joy of dreaming about a new life in another place.

What an odd question!

Edit: My ideal temperature range left me with just Vancouver, Canada.

Vancouverite here - the temperature is quite moderate but you need to be okay with a lot of grey drizzly days. Summers are wonderful though.