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Preparing for Heat Waves in Chicago

“I vividly recall the intense heat that surrounded me. The constant warnings on television urged us to stay home with air conditioning and stay hydrated. Venturing outside was a brief sprint from door to car, as even those few meters exposed us to unbearable heat. The city had even repurposed public buildings, malls, and buses with air conditioning to accommodate those without appropriate housing conditions.”

Sara Baudoux - About visiting Chicago in the 1990s

A heat wave, or extreme heat event, is defined by the Intergovernmental Panel on Climate Change as a “period of abnormally hot weather” lasting for at least two days, that often comes with high humidity. However, what temperature threshold marks a heatwave varies by region. In the Great Lakes area, the definition of a heat wave usually includes three straight days of temperatures in the 90°F or higher.

The frequency of extreme heat events in US cities has steadily increased over the years. In the 1960s, there were an average of two heatwaves per year, which rose to six per year in the 2010s. The heat wave season now lasts 49 days longer compared to 60 years ago. This trend is particularly prominent in the Chicago area. Chicago is also impacted by the urban heat island effect, where the city retains more heat than the surrounding areas during the day and especially at night. Heatwaves are the primary cause of weather-related deaths in the US.

The July 1995 Chicago heat wave was a disastrous heat wave that led to the death of 739 persons in 5 days. This event had a disproportionate impact on certain communities. Elderly individuals residing in impoverished and unsafe neighborhoods faced significant challenges, as they hesitated to open their windows, fearing for their safety. Moreover, those who couldn’t afford air-conditioning experienced severe disadvantages. Notably, the mortality rate was disproportionately higher among Black residents due to disparities they faced in their communities.

The urban heat islands effect played a significant role in the soaring temperatures, particularly at night when when absorbed daytime heat was released. Due to historical inequities such as redlining, urban heat islands are more likely to be found in communities of color and those where residents make lower incomes. Environmental injustice was an important aggravating factor in this extreme weather event.

The enduring effects of redlining are highly noticeable in US cities. Disinvested neighborhoods, lacking green spaces and adequate infrastructures, experience significantly higher temperatures. According to a study, historically redlined areas can be 5 to 20°F warmer than non-redlined neighborhoods.

Urban trees play a crucial role in regulating surface and air temperatures through evapotranspiration and shading. Evapotranspiration includes the process of water evaporation from soil as well as the process by which water is released into the atmosphere from plant leaves in a way that cools the surrounding atmosphere. Planting trees is an effective way to mitigate the urban heat island effect, with shaded areas being as much as

45°F cooler than exposed surfaces. Moreover, evapotranspiration aids in reducing summer peak temperatures by 2 to 9°F. In the United States, they can significantly lower air-conditioning expenses by 20 to 30 percent. Trees also contribute to carbon sequestration and mitigate air pollution, improving our health and our environment.

Adopting proactive measures to mitigate the impact of heat waves is vital to increase social justice and climate resilience. Apart from planting trees, other adaptive measures also prove effective in cooling urban areas. Some examples include white and green roofs as well as wind corridors. Wind corridors are areas where significant and consistent airflows occur. Light-colored roofs help reflect heat and green roofs provide shade and cooling. Access to air conditioning is crucial during heat waves, and public cooling centers can help address socio-economic disparities. Staying informed by checking weather forecasts is essential, as is checking on the well-being of friends, family, and elders. The American Red Cross website offers an "Extreme Heat Safety" page for valuable information on staying safe and treating heat-related illnesses.

As heat waves become more frequent and intense, it is crucial for communities to adapt and prepare for extreme temperatures both now and in the future.

Building cooler, safer cities through adaptive measures can help prevent tragic losses like those experienced during the 1995 Chicago heat wave. Planting trees, and expanding green spaces like parks and gardens can help cities effectively reduce urban heat island impacts. Trees, in particular, offer a nature-based solution with multiple benefits to community health and well-being. Being mindful of environmental justice and incorporating community voices when planting trees is increasingly important, given the disproportionate impact of the climate crisis on our most vulnerable populations.

Nordson Green Earth Foundation’s Cook County Markham Courthouse Tiny Native Forest. The first public MIYAWAKI forest in Illinois.


References and further readings :

Kaiser et al., (2007). The effect of the 1995 heat wave in Chicago on all-cause and cause-specific mortality.

American journal of public health.

MRCC. (2023). Heat Waves. Midwestern Regional Climate Center.

Palmer & Popovich. (2020). How decades of racist housing policy left neighborhoods sweltering. New York Times.

UN Environment Programme. (2019). From heatwaves to rising seas: How trees defend us. UNEP.

United States Environmental Protection Agency . (2022). Heat Islands. EPA.

The American National Red Cross. (2023). Extreme heat safety. Heat Exhaustion Safety | Red Cross.

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