My friend Jeff obstinately uses Celsius units when describing the weather regardless to whom he's talking. Celsius might be one of the most difficult of day-to-day Metric units for an American because most of us have no clue what to wear based solely on a Celsius reading of the temperature. Is 20° C hot or cold? Most of us don't know without performing a conversion to Fahrenheit first. As it turns out, 20° C is a pleasant 68° F.
Jeff's independent change of habit to using metric temperature units inspired me to do the same; I reconfigured the weather widget on my Google homepage to display metric units. Doing so has increased my familiarity with the range of temperatures from 30° C to 45° C this summer but has done little else to spark a greater comfort with the Celsius unit.