But in my recent trip to Australia, I finally worked out the the amazingly simple "rough guide to Celcius".
From zero to 10, wear a coat.
From 10 to 20, wear a jacket.
Room temperature is 20.
From 20 to 30, wear a shirt.
From 30 to 40, it's hot.
And 40 and above, find an AC before you heatstroke.
That wasn't hard at all.