Extreme Heat Events and Public Health: (b1.2) Age-Children: Research identifies children, especially children ages five years and younger (including infants), as being at a greater risk for mortality during hot weather. Children may be at increased risk due to dependency on other people for their care and/or physiological differences, including smaller body mass to surface area ratio than adults, blunted thirst response, production of more metabolic heat per pound of body weight and lower cardiac output. In the US between 1998 and 2011, an average of 38 children (five days old to 14 years old) died per year from being left in a motor vehicle during warm weather. More than half of the deaths are children under two years of age. Temperatures in parked cars can increase quickly even on relatively mild days (i.e., ~ 70°F), especially if the car is parked in the sun. Leaving the windows slightly open does not significantly decrease the heating rate. For a short video demonstrating how quickly temperatures can increase in a parked car, see the following website: http:// www.nws.noaa.gov/os/heat/index.shtml. Never leave children, infants or pets unattended in a parked vehicle. (b1.3) Economic Constraints: Several studies have demonstrated increased risk of mortality among people with low socioeconomic factors. Persons living at or below poverty line are less likely to have air conditioners in their homes, live in deteriorating and substandard homes, and may have difficulty paying for higher electricity bills from increased electricity usage during an extreme heat event. Persons living at or below the poverty line might be more concerned about safety and unwilling or unable to seek cooling centers or open doors and windows to increase circulation. The homeless are at increased risk for illnesses and death due to extreme heat possibly because of limited access to air‐conditioned places and underlying medical conditions. (b1.4) Persons with Pre-Existing Diseases or Mental Health Conditions: Heat can exacerbate existing conditions, putting certain people at increased risk for heat‐related illnesses and possibly death. Any condition that affects the body’s ability to cool itself or puts additional stress on already compromised systems will make a person more susceptible to negative health effects from heat. Pre‐existing conditions that make a person more vulnerable to extreme heat include obesity; cardiovascular disease conditions (e.g., congestive heart failure, myocardial infarction); respiratory disease conditions (e.g., COPD, bronchitis); neurological diseases; endocrine disorders (e.g., diabetes mellitus); renal failure; and liver diseases (e.g., liver cirrhosis). Additionally persons with mental illness or intellectual disabilities are at increased risk for negative health outcomes due to extreme heat. They may be unable to make rational decisions that would help them recognize symptoms of or limit their exposure to excessive heat. (b1.5) Persons on Certain Medications: Persons on certain medications are vulnerable to negative health consequences from extreme heat events. Drugs, such as diuretics, anticholinergics, beta blockers and calcium channel blockers and antipsychotic drugs, make it difficult for the body to dissipate excess heat by interfering with normal thermoregulatory systems. For a complete list of categories of medicines that may increase a person’s risk of heat‐related illness, see Appendix B. (b2) Social/Behavioral Factors: (b2.1) Social Isolation: Persons living alone, especially the elderly, are more vulnerable to extreme heat events. Socially isolated people may be less likely to recognize the symptoms of excessive heat exposure, less likely to leave their homes if hot, and/or less willing or able to reach out for help from others. (b2.2) Prolonged Exposure to Sun: People who are involved in sporting activities or work in outdoor occupations, like farming, landscaping, roofing, and construction, are at an increased risk for heat‐ related illnesses. These people may be exposed to the sun and extreme heat for longer periods of time and need to take extra precautions to stay cool and hydrated. (b2.3) Use of Alcohol and Drugs: The consumption of alcoholic beverages during extreme heat events increases the risk of heat‐related illnesses. Alcoholic beverages can cause dehydration and depress the thermoregulatory system. In addition, alcohol and drugs impair judgment, influencing a person’s ability to make decisions to limit exposure to and recognize symptoms of extreme heat exposure. (b3) Geographic/Location factors: (b3.1) Living in Urban Areas: The urban heat island effect is a measurable increase in ambient urban air temperature and results primarily from the replacement of vegetated land with buildings, roads, and other heat‐absorbing and reflecting infrastructure. Urban dwellers are more at risk for heat‐related illnesses than rural dwellers because of the urban heat island effect. Urban areas are usually hotter and cool off less at night than rural areas. The annual mean air temperature of a city with 1 million people or more can be 1.8–5.4°F warmer than its surroundings. In the evening, the difference can be as high as 22°F. The urban heat island effect is proportional to the size of the city, but all cities, large and small experience the effect. Urban heat islands can increase health risks from extreme heat by increasing the potential maximum temperatures residents are exposed to and the length of time that they are exposed to elevated temperatures. (b3.2) Lack of Air Conditioners: Living in houses without air conditioning and/or not having access to air conditioned spaces increases the risk of experiencing heat‐related illnesses. During periods of extreme heat, air conditioners regulate and cool indoor air temperatures, putting less strain on the body’s thermoregulatory system. (b3.3) Living in Top Floor Apartments: Persons living in top floor apartments are at increased risk of suffering from heat‐related illnesses. Hot air rises and is trapped by the roof, so that people who live on the top floors of a building are exposed to higher temperatures. (b3.4) Living in Nursing Homes/Bedridden: Persons living in long‐term care facilities (e.g., nursing homes, assisted living, group homes) and/or are bedridden are at increased risk of suffering from heat‐related illnesses. These persons may be at increased risk due to dependency on others for care, and they frequently have underlying medical conditions and take medications that affect their ability to regulate their body temperature