College of Agriculture & Natural Resources
Agricultural & Resource Economics

The Risks of Summer Heat

UMD AREC to Study Climate Change and Its Impact on Vulnerable Persons in Maryland
100 degree thermometer

The department is pleased to announce a new undergraduate research project about climate change and vulnerable persons in Maryland funded by and conducted within AREC. Look for more information on this web site in the next few weeks. In the meantime, here's what summer heat may mean...


The Intergovernmental Panel on Climate Change (2014) warns that as the earth gets warmer we can expect temperate regions to experience more frequent and intense heat waves. Excessive heat episodes are also expected to last longer, and may be accompanied by poor air quality. The associated health risks are most serious for people with respiratory and cardiovascular conditions, persons with inadequate housing, children, persons who must take certain types of medication, the poor and people who must work outdoors.

Heat worsens pre-existing conditions more often than it kills. People end up at the hospital because of extreme heat, but there’s an undercount of cases where heat is a factor. In fact, a lot of cases are coded as something else.

The High Country News, a periodical about environmental, social and economic issues in the American West, recently published an article entitled “The Danger of Urban Heat,” that documents the experience of Latino families in relatively poor neighborhoods in Los Angeles. The author of the article, Molly Peterson, describes the difficulties of 17-year-old Edwin Diaz, who suffers from debilitating migraines that tend to get worse when the temperature climbs into the 90s. Diaz does not have air conditioning at home and his home is poorly insulated. Many other dwellings in the neighborhood were created by dividing existing homes or converting garages. They often lack windows, let alone air conditioners, and are surrounded by paved surfaces, which tend give out heat even as the sun sets. Mayor Eric Garcetti has set the goal to lower the city’s urban heat island’s temperature by 3 degrees in 20 years, and the Los Angeles Office of Sustainability is studying landscaping solutions to help reach this goal.

This summer Southern California has experienced a number of extremely hot days and the same extended heat wave that affected Phoenix and much of Arizona.  The Maricopa County Health Department in Phoenix has tracked heat-related deaths for more than 10 years. All the cases are broken down by different criteria such as age, ethnicity, etc. Together with the Arizona State University and Los Angeles, it is trying to understand how counteract heat-related sickness and death. Peterson reports that deaths caused by heat are climbing in Phoenix, but the reasons are still unknown. Without knowing the causes behind it, officials say, it’s almost impossible to find a strategy to defeat it. See the Arizona Department of Health web site about extreme weather and public heath for more information.

And most recently temperatures have been in the double digits in the Pacific Northwest, where it is estimated that only some a small share of the homes have air conditioning.  

So what do local governments do to protect residents when the weather is too hot? The District of Columbia issues heat advisories, which are posted on the city’s web site and sent via text messages to residents who subscribe to the city’s alert system. Here’s an example of one such text from this summer:

“The National Weather Service (NWS) reports the temperature is 89 degrees with a HEAT INDEX of 98 degrees. The Department of Human Services (DHS) has activated the Heat Emergency Plan. MPD, FEMS, DDOT and the Ward Outreach have been notified. 

As temperatures rise, the District of Columbia Fire and Emergency Medical Services Department and DC Water urge those in the District to beat the heat without tampering with fire hydrants. Unauthorized hydrant use can hamper firefighting, damage the water system and cause injury. It can also flood streets, creating traffic dangers and it can lower the water pressure for everyone on the block.

Residents and visitors in the District can keep cool by staying in shade or air conditioning and drinking plenty of water. When the temperature or heat index reaches 95, residents are encouraged to take extra precautions against the heat. If they do not live in an air-conditioned building, they may take refuge at a District indoor swimming pool, spray parks, cooling center, recreation facility, senior center or other air-conditioned building. More information, and locations, can be found at or by contacting the heat hotline at 202-399-7093.”

The web site provides a list of swimming pools, spray parks (with misters), and “cooling centers” (usually public buildings or libraries with air conditioning where people can take a break from the heat). The city of Baltimore offers similar options.  

Some cities have a proactive approach to managing heat-related health risks, and encouraging neighborhood “captains” (contact persons) to keep track of the elderly, those with physical impairments, those with no air conditioning, and other vulnerable persons. They often encourage the so-called “buddy system,” where elderly persons call on each other on a regular basis on the hottest day to make sure that they are doing fine.

But the heat is not the only cause for concern. Heat waves are often accompanied by bad air quality episodes. As with heat waves, cities and the National Weather Service post warnings to help residents stay healthy. In the Washington DC and Baltimore area, bad air quality means unhealthful levels of tropospheric ozone, a pollutant that is created when nitrogen oxides (emitted by power plants and cars) and volatile organic compounds (emitted by cars and certain manufacturing facilities) react to ultraviolet radiation and heat. Here is an example of a warning: 

“This is an important message from the District of Columbia AlertDC system.

The National Weather Service (NWS) reports the Air Quality Alert is in effect for Friday, July 21, 2017. The Metropolitan Washington Council of Governments in association with Maryland Department of the Environment, Virginia Department of Environmental Quality, and District Department of Environment has issued a Code ORANGE Air Quality Alert for the DC metro area.

A Code Orange Air Quality Alert means that air pollution concentrations within the region may become unhealthy for sensitive groups. Sensitive groups include children, people suffering from asthma, heart disease or other lung diseases and the elderly. The effects of air pollution can be minimized by avoiding strenuous activity or exercise outdoors.”

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