I thought it was slightly ironic that I would have a case of SIWOTI Syndrome with xkcd itself, which is why I thought I'd set the record straight. While I appreciate the sentiment of the Converting to Metric comic, I think it should be pointed out that -10 degrees Celsius is not a cold day in Moscow. Having lived there for two years, I think it should be pointed out that days don't start being regarded as cold until you go below -20 or -25, and actually cold days are in the -30s. My school had a rule that it would be cancelled if the temperature ever hit -40, but, sadly for me, the coldest winter day I experienced in my two years there was -39.5.
Funnily enough, I have a story about -10 and Moscow. When my Argentinian brother-in-law was visiting my family in Moscow, he found it awfully cold (he would agree with xkcd that -10 was a cold day, despite what the Russians and Canadians might say). One day he was out with my sister and my parents (it was -10 degrees C at the time) and he spotted a band of Russian fellows in the park practicing soccer. He was quite horrified, explaining that he would not practice if it were 10 degrees outside since that would be too cold. So, I suppose what is cold is a little relative, but if one is going to tabulate a chart of reference points, the "Cold Day (Moscow)" entry should be adjusted to a slightly more accurate value.