Many people do not realize how deadly a heat wave can be. In contrast to the visible, destructive, and violent nature of floods, hurricanes and tornadoes, heat waves are “silent killers.” More people die in an average year in Kansas City from heat-related conditions, than from all other weather types combined. According to the Center for Disease Control, an average of 350 people die from the effects of heat in the U.S. each year.
What is a heat wave?
A heat wave is a period of excessive heat lasting two days or more. High humidity, which often accompanies heat in the Midwest, can make the effects of heat even more harmful. While heat-related illness and death can occur due to exposure to intense heat in just one afternoon, heat stress on the body has a cumulative effect. Consequently, the longer a heat wave lasts, the greater the threat to public health.
The “heat-island” effect
Most heat-related deaths occur in cities. Brick and mortar buildings, asphalt streets, and tar roofs absorb daytime heat and slowly release it at night. Consequently, temperatures in urban areas can be warmer than rural areas by several degrees both day and night. This is commonly called the urban “heat-island” effect. In addition to the burden of heat, stagnant conditions often develop during heat waves, with pollutants increasing in concentration near the ground and contributing further to public health problems during heat waves.
Who is most vulnerable during a heat wave?
The elderly are most vulnerable to the dangers of heat, due to a diminished ability to perspire. Perspiration provides evaporation, which in turn provides cooling, so the elderly have a reduced capacity to release heat from the body.
In addition to the elderly, infants, young children, and people with chronic health problems (especially pre-existing heart disease) or disabilities are more vulnerable to the effects of heat waves. People who are not acclimated to hot weather, overexert themselves, are obese, or use alcohol or drugs are also at greater risk.
Measuring the combined effects of heat and humidity
The National Weather Service uses the Heat Index to compute the “apparent temperature,” which is a measure of how hot it feels to people at a certain combination of temperature and humidity. The greatest number of heat-induced illnesses and fatalities from a heat wave usually peak two days after the maximum heat index values occurred.
The National Weather Service issues a Heat Advisory when a heat index of 105° will be reached for at least three hours, with little cooling expected overnight. A Heat Warning is issued if the heat index will reach 105° for three days or more, or if the heat index will reach 115° on a single day.
Heat Safety Tips
- Drink plenty of water and natural fruit juices, even if you’re not thirsty. Avoid alcoholic beverages, sweetened beverages and drinks with caffeine, such as coffee, tea and colas.
- Wear loose-fitting, lightweight, light-colored clothing. If you must go out, use sunscreen and wear a wide-brimmed hat. Remember that sunburn reduces the skin’s ability to provide cooling.
- Avoid going out during the hottest times of the day. Take frequent breaks if working during the heat of the day.
- Use a buddy system between co-workers in high heat-stress jobs to help ensure that signs of heat stress do not go unnoticed.
- Inside during the day, keep shades drawn and blinds closed. Use air conditioning whenever available. Even just two hours per day in air conditioning can significantly reduce the risk of heat-related illness.
Fans should only be used in a ventilated room. Blow hot air out a window with a fan during the day, and blow cooler air in at night.
- Take cool (not icy cold) baths or showers. Eat frequent, small meals. Avoid high-protein foods, which increase metabolic heat. Fruits, vegetables, and salads constitute low-protein meals.
- Do not leave children or pets in a closed vehicle with the windows up. Temperatures inside a closed vehicle can reach over 140° within minutes.
- Provide extra water and access to a cool environment for pets.
- Listen to your NOAA Weather Radio or media sources to keep up with the latest heat watches, warnings, and advisories.