by Donald Long, Pathways Intern, NWS Chicago
A potent combination of heat and moisture created lethal conditions throughout Chicagoland during the summer of 1995, especially from July 11 to 17.
Despite having some anticipation of record high temperatures, Chicagoans were ill-equipped to combat the mid-July heat wave. The “American Journal of Public Health” estimates that 739 lives were claimed by the oppressive heat.
The lessons learned from this tragedy revolutionized how the National Weather Service (NWS) in Chicago communicates hazardous weather to city officials as well as how the city prepares for and responds to hazards. In fact, this partnership between the city and NWS Chicago remains one of the premier examples of the Weather Ready Nation initiative, which stresses that a forecast is only valuable when users understand it and respond appropriately.
Meteorological Synopsis. A very warm, moist air mass had set up over the Midwest on July 12, 1995. The high moisture content was exacerbated due to evapotranspiration from crops across the Corn Belt. An upper-level anticyclone funneled warm air into the region while simultaneously forcing it to stay near the ground. The sum of all these factors resulted in heat indices in excess of 100 F between July 12 and 16, overnight low temperatures that were near normal daytime high temperatures for this time of year, and an all-time record high temperature of 106 F at Midway Airport on July 13.
Then and Now—What We Learned. Residents’ social isolation for fear of crime, inexperienced city officials, and a general lack of respect for heat led to the tragic outcome. In the wake of the disaster, the way Chicago planned for emergencies, even beyond heat-related events, was completely overhauled. The NWS and city drafted Chicago-specific heat warning criteria that included sustained heat parameters for one, two, or three days. Along with these new criteria came new procedures for how to manage extreme heat and other crises that may affect Chicago. A direct hotline was also established between the NWS and the Chicago Office of Emergency Management and Communications (OEMC). These strides towards a preventative approach to public safety are used today and reviewed often so that they are up to date.
Summary. NWS Chicago works closely with the city in a variety of weather conditions and situations. Though the 1995 heat wave shook the city to its core, examples of the lessons learned and the newfound commitment to public safety are present today. These include relatively limited impacts from the infamous 2011 Groundhog Day blizzard, minimal loss of life during the 2019 record cold outbreak, and recent large-scale event evacuations (such as Lollapalooza) due to inclement weather that were executed without incident. While the heat wave tragedy was brought about by significant heat and moisture and exacerbated by a lack of preparedness, great strides to improve preparedness and communication were made immediately following the event. The NWS and the City of Chicago continue to work together closely as part of a large network of preventative measures designed to keep Chicagoland safe.