July Fourth Heat and Your Health

Patricia Yarberry Allen, M.D. is a Gynecologist, Director of the New York Menopause Center, Clinical Assistant Professor of Obstetrics and Gynecology at Weill Cornell Medical College, and Assistant Attending Obstetrician and Gynecologist at New York-Presbyterian Hospital. She is a board certified fellow of the American College of Obstetrics and Gynecology. Dr. Allen is also a member of the Faculty Advisory Board and the Women’s Health Director of The Weill Cornell Community Clinic (WCCC). Dr. Allen was the recipient of the 2014 American Medical Women’s Association Presidential Award.

The fireworks may not be all that we see in the sky this Fourth of July as much of the country deals with prolonged and excessive heat due to a “heat dome.” A sprawling and unusually intense area of high pressure, aka the “heat dome,” will promote sinking air and sunny, storm-free conditions for the areas it covers, according to Accuweather.

July is typically the hottest month of the year for the U.S. and this year it is going to start off scorching across the country as a dangerous heat wave stretches from Arizona to Maine. The heat and humidity will combine to create life-threatening conditions in many cities, particularly in the Midwest and Northeast, where heat advisories and excessive heat warnings are in effect. Up to 18 states have already issued heat advisories, according to the National Weather Service. Officials have warned that the hot and humid weather is expected to persist during and after the Fourth of July holiday on Wednesday.

When people are exposed to extreme heat, they can suffer from potentially deadly illnesses, such as heat exhaustion and heat stroke. Hot temperatures can also contribute to deaths from heart attacks, strokes, and other forms of cardiovascular disease. Heat is the leading weather-related killer in the United States, even though most heat-related deaths are preventable through outreach and intervention (see the EPA’s Excessive Heat Events Guidebook.)

“Heatstroke” is a common term used to describe two distinct entities: (1) severe non-exertional hyperthermia (overheating of the body), which generally affects the very young, the disabled, the poor, those who are isolated because of mental illness, or the elderly; and (2) exertional heat illness, which mostly affects otherwise healthy adults and adolescents. These two groups are linked due to underlying causes and effects (too much heat or sun exposure and a lack of hydration) and the future health impact (extreme elevations of body temperature leading to bodily dysfunction).

Heat exhaustion sometimes occurs when a person exercises and works in a hot environment and the body cannot cool itself adequately. Dehydration happens with water loss from excessive sweating, which causes muscle cramps and weakness, along with nausea and vomiting. This makes it difficult to drink enough fluid to replenish the body’s water supply, and the lack of body water impairs further sweating, evaporation, and cooling. If the humidity is too high, sweat on the skin cannot evaporate into the surrounding air and body temperature cooling fails.

Heat exhaustion and heatstroke are caused by environmental conditions. As outside temperatures rise, the body reacts by sweating. This evaporation of water from the skin and respiratory tract is the most effective way of ridding the body of excess heat. Less effective reduction in temperature occurs from the direct radiation of heat into the environment, the transfer of heat to air or liquids moving over the body. These normal cooling mechanisms become ineffective when humidity rises above 75%, and air temperature rises above normal body temperature.

Prevention begins with awareness of one’s environment and altering behaviors that increase the risk of heatstroke when at all possible.

1. Avoid strenuous activities in excessively hot or humid climates.
2. If work must be done in the heat outdoors, or indoors in hot situations, take frequent breaks in cooler areas, spray the skin with water, drink water and sports drinks to replace lost electrolytes from sweating, monitor urine output, and slow the pace of work to decrease the heat generated by the body to avoid heat exhaustion or heatstroke. Avoid the sun from 11 a.m. to 3 p.m. when at all possible.
3. Monitoring urine output is an effective way to monitor hydration. The kidneys hold onto water if the body is dehydrated, then urine output drops and the urine becomes darker with a strong odor. When hydration is adequate, the urine is clear and normal in amount.
4. Avoid caffeine and alcohol since these promote dehydration. Alcohol lowers the body’s tolerance for heat as well as acting as a diuretic.
5. Do not move from a cool to a very hot environment quickly since this prevents the body from adjusting to allow it to cool more efficiently. Moving from hot weather to a cold environment can also be dangerous because of the extremely rapid change in the body temperature.
6. Pay attention to those at risk during heat waves: the elderly, the obese, the socially isolated, the very young and those who have no air conditioning to cool their homes. Make certain that they are well hydrated and not alone. Move people to cooling centers if there is one in your area or bring them to a public place where air conditioning exists.

Recognize the most common signs and symptoms of heat exhaustion to get treatment early to prevent heat stroke.
1. Confusion
2. Dark-colored urine (a sign of dehydration)
3. Dizziness
4. Fainting
5. Fatigue
6. Headache
7. Muscle or abdominal cramps
8. Nausea, vomiting or diarrhea


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  • Gail Willis July 4, 2018 at 2:53 am

    Trying to only laugh sympathetically. This is only slightly less awful than my experience at the Quality Inn adjacent to the Newark airport several years ago. Ours varied – with freezing temperatures instead of heat and exposed ‘live’ wiring throughout the unit. This,with two non-stay over experiences, are why I vow never ever to fly into Newark again.