Even more curious is the distribution of Melbourne's hot and cold days, as reflected in this chart for the years 1986-1991:
Just as in the first chart, the pattern of a narrow temperature band in the winter and a much wider range of temperatures in the summer is noted. What is particularly striking about the summer pattern is the "hole" separating the relatively clustered cooler-than- average temperatures below the solid line and the greatly scattered warmer-than-average temperatures above the solid line. Statisticians refer to such a pattern as "bi-modal". Hot days are usually followed by hot days or by cool days but rarely by anything in between. Melbourne summer is Jekyll or Hyde.
But is it hot very often? This chart is based on weather data as cited in a
presentation from Monash University, and covers the dates of the Australian Open Tennis
January in Melbourne, which corresponds to July in the northern hemisphere, is usually mild. 65% of daily high temperatures are less than 80°F, and only 1% of temperatures exceed 104°F. This frequency distribution may explain the Australian Open's choice of heat standards: The organizers could simultaneously tell the medical community that they were giving due consideration to the hazards of heat injury and they could reassure their TV and other sponsors that there was a 99% chance that the Rule would not be invoked.
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