Extreme heat is one of the deadliest weather-related hazards in the United States. During
periods of prolonged heat, especially when humidity is high, the body can struggle to cool itself,
increasing the risk of heat cramps, heat exhaustion, and heat stroke.

Recognizing Extreme Heat Risks
Protecting yourself during hot weather includes limiting strenuous activity during the hottest
parts of the day, seeking shade or air-conditioned spaces, wearing lightweight clothing,
checking on vulnerable neighbors, and staying alert for signs of heat-related illness. Fatigue,
nausea, headache, cramps, paleness and sweating are signs of heat exhaustion. Body
temperature over 103 degrees, red, hot, dry skin and rapid pulse along with worsened confusion
and loss of consciousness are signs of heat stroke, a medical emergency. Call 911 or go to the
hospital immediately.

Source: https://www.ready.gov/sites/default/files/2024-03/ready.gov_extreme-heat_hazard-info-sheet.pdf

Reducing Extreme Heat Risks
One of the most important ways to reduce risk is maintaining adequate hydration,
particularly during periods of extreme heat. Signs of dehydration are headache, cramps, and
thirst, but by the time you have these symptoms, you are already missing 2-3 liters of fluid. Try
these tips for hydration.

People at Increased Risk for Heat Illness
Some groups of people are more vulnerable to heat illness than others. Older adults,
young children, people with chronic medical conditions and mental illness, outdoor workers, and those without access to air conditioning are at greater risk. In older adults, the body's ability to regulate temperature and sense thirst becomes less effective They often sweat less efficiently and may not notice thirsty until they are dehydrated, in part due to cognitive problems. Blood vessels may also respond more slowly to heat, making it harder for the body to release excess heat.
People living with serious mental illnesses such as schizophrenia, bipolar disorder, or severe
depression are less tolerant of heat just from their illnesses. Some psychiatric medications
can interfere with sweating, thirst perception, or the body's ability to regulate
temperature. Certain neurological, developmental, or physical disabilities may also affect
temperature perception, sweating, or the ability to communicate distress. These factors can
delay recognition of dangerous heat exposure. People who live alone may also have no one to
notice worsening symptoms or provide assistance during heat emergencies. Regular check-ins
from family, friends, or neighbors can help prevent serious outcomes. Social contact increases
the likelihood that early warning signs will be noticed and addressed before an emergency
occurs.

Chronic medical conditions, medications, and reduced mobility can also make it harder to
stay cool and hydrated, in elders as well as others. Conditions such as heart disease, lung
disease, diabetes, and kidney disease can reduce the body's ability to respond to heat stress. Some medical conditions also increase the risk of dehydration or make heat-related symptoms more dangerous. Many chronic illnesses affect circulation, fluid balance, or the body's ability to maintain a stable internal temperature. Heat places additional demands on organs that may already be working harder to compensate for disease.

Some medications can interfere with sweating, hydration, or temperature regulation.
Others may increase sensitivity to heat or contribute to fluid loss. For example, diuretics
increase water loss, while some psychiatric, antihistamine, and blood pressure medications may
reduce sweating or alter heat perception. These effects can impair the body's natural cooling mechanisms during hot weather.

Children have a larger body surface area relative to their body weight, so they absorb heat
faster. Their sweating mechanisms are also less developed than those of adults, reducing their
ability to cool themselves effectively. They also depend on caregivers to provide fluids, shade,
and appropriate clothing.

People who work outdoors may spend long periods exposed to high temperatures and direct
sunlight. Physical exertion generates additional body heat. Exercise raises body temperature
and increases fluid loss through sweating. During hot weather, intense activity can overwhelm
the body's cooling mechanisms if adequate rest and hydration are not maintained. In hot or
humid conditions, evaporation of heat by sweating is less effective, increasing the risk of
overheating. Prolonged exposure to high indoor or outdoor temperatures also limits
opportunities for the body to cool down. The body benefits from periods of cooler
temperatures, especially at night, to recover from daytime heat exposure. Heat can
accumulate over several days, increasing the risk of serious illness.

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Finally, pregnancy increases metabolic demands and can make it more difficult for the body to
dissipate heat. Pregnant individuals generate additional body heat as the body supports fetal
growth and increased blood volume. The cardiovascular system is already working harder
during pregnancy, leaving less reserve for coping with extreme heat. Dehydration and
overheating may affect both maternal and fetal health.