Shown in Figure 1a are the fractions of respondents that opened a window “yesterday”as a function of the maximum temperature in that location, averaged over the entire US, in4°C intervals. The size of the symbols is related to the number of respondents; therefore, re-sults above 0°C have a higher degree of certainty than those below -6°C. Window openingpeaks at 60% between 22-26°C,