The 1995 Chicago Heat Wave: How Likely Is a Recurrence?

Abstract

Abstract The deadly heat wave of July 1995 that affected much of the U.S. midwest, most notably Chicago, Illinois, has been put into historical perspective. The heat wave has been found to be remarkably unusual, but only partially because of the extreme high apparent temperatures (an index of the combined effect of temperature and humidity on humans), where the authors calculate a return period of the peak apparent temperature of ≤23 yr. Of greater significance were the very high temperatures that persisted day and night over an extended 48-h period. Analysis presented here indicates that for Chicago such an extended period of continuously high day and night apparent temperature is unprecedented in modern times. The 2-day period where the minimum apparent temperature failed to go below 31.5°C (89°F) is calculated to be an extremely rare event (probability of occurrence <0.1%) based on a 10 000-yr-long simulation of a four-parameter (temperatures related to the mean, the intraseasonal daily variance, the i...