In the past, when talking with someone from the non-US rest of the world and they would give a temperature in degrees Celcius, I would have to quickly do the mental math to convert to degrees Farenheit to get a sense of how warm or cold they were describing.
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.
