Heat Safety: A Complete Guide from MWN

Many Memphians are aware of, or experienced, the record-breaking heat of the summer of 1980, even though it was 35 years ago this summer. The longest streak of 90-degree temperatures in Memphis recorded history was July 25-September 16, 1980 (54 days). Just prior to that, the longest recorded streak of 100-degree days occurred, a 15-day stretch from July 6-20, 1980, including the all-time record high of 108°F set on July 13, 1980. Eight July days still have high temperature records set that year and 12 July days have maximum low temperature records, all of them at or above 82°F (Source: http://www.memphisweather.net/alltime-shtml).

A graph of observed temps (blue bars) for July 1980 in Memphis shows just how hot it was that month. Many days set record highs (red line) with temperatures above 100° and low temperatures frequently above 80°.

The hot weather of July 1980 resulted in 83 deaths in Memphis and at least 1,700 nationwide during that summer. This heat wave tragically demonstrated that heat and humidity can be a deadly combination. These factors put a lot of stress on the human body and can lead to serious health conditions such as heat exhaustion, heat stroke, or even death. The more extreme the temperature, the shorter the amount of exposure time needed to fall ill.

The Dangers of Excessive Heat

Heat waves have the potential to cover a large area, exposing a high number of people to a hazardous combination of heat and humidity. In fact, heat is typically the leading cause of weather related fatalities each year, averaging 123 deaths per year from 2004-2013 and even more heat-related illnesses. From 1998-2014, an average of 37 children nationwide have died each year from heat stroke in a vehicle. High temperatures and humidity, and thus heat-related illness, are common in the Mid-South.

Heat Index - a measure of how hot it feels

The Heat Index is a measure of how hot it really feels when relative humidity is factored in with the actual air temperature. To find the Heat Index temperature, look at the Heat Index Chart below or check this Heat Index Calculator. As an example, if the air temperature is 96°F and the relative humidity is 50%, the heat index - how hot it feels - is 108°F. The red area without numbers indicates extreme danger.

The National Weather Service in Memphis issues a Heat Advisory when the Heat Index is expected to peak between 105°F-109°F.  An Excessive Heat Watch is issued when, 24-72 hours in the future, the Heat Index is expected to exceed 110°F and overnight low temperatures will be above 75°F. An Excessive Heat Warning is issued when the Watch criteria above are occurring or imminent (within 24 hours). Since heat index values were devised for shady, light wind conditions, exposure to full sunshine can increase heat index values by up to 15°F.

Heat Safety Tips

Here are some hot weather safety tips to consider during the "dog days" of a Memphis summer:

• Slow down! Reduce, eliminate or reschedule strenuous activities until the coolest time of the day. Children, seniors and anyone with health problems should stay in the coolest available place, not necessarily indoors.
• Dress for summer. Wear lightweight, loose lifting, light-colored clothing to reflect heat and sunlight.
• Eat light, cool, easy-to-digest foods such as fruit or salads.
• Drink plenty of water (not very cold), non-alcoholic and decaffeinated fluids, even if you don't feel thirsty. If you on a fluid restrictive diet or have a problem with fluid retention, consult a physician before increasing consumption of fluids.
• Use air conditioners or spend time in air-conditioned locations such as malls and libraries.
• Use portable electric fans to exhaust hot air from rooms or draw in cooler air.
• Do not direct the flow of portable electric fans toward yourself when room temperature is hotter than 90°F. The dry blowing air will dehydrate you faster, endangering your health.
• Minimize direct exposure to the sun. Sunburn reduces your body's ability to dissipate heat.
• Take a cool bath or shower.
• Do not take salt tablets unless specified by a physician.
• Check on older, sick, or frail people who may need help responding to the heat. 
• Keep your children, disabled adults, and pets safe during tumultuous heat waves. Make sure outdoor pets have a shaded place to stay and that they have plenty of fresh water.

Parents, here are additional tips as you care for children in hot weather:

• Touch a child's safety seat and safety belt before using it to ensure it's not too hot before securing a child
• Never leave a child unattended in a vehicle, even with the windows down, even for just a minute
• Teach children not to play in, on, or around cars. They could accidentally trap themselves in a hot vehicle.
• Always lock car doors and trunks - even at home - and keep keys out of children's reach.
• Always make sure children have left the car when you reach your destination. Don't leave sleeping infants in the car ever!

Graph courtesy NoHeatStroke.org showing how fast an enclosed vehicle heats up. 

Even on mild days in the 70s, studies have shown that the temperature inside a parked vehicle can rapidly rise to a dangerous level for children, pets and even adults. Leaving the windows slightly open does not significantly decrease the heating rate. The effects are more severe on children because their bodies warm at a rate 3-5 times faster than adults. A dark dashboard or carseat can quickly reach temperatures in the range of 180°F to over 200°F. These objects heat the adjacent air by conduction and convection and also give off long wave radiation, which then heats the air trapped inside a vehicle. For more information on preventing children's deaths due to heat stroke, visit NoHeatStroke.org or download this fact sheet (PDF).

Heat Illnesses

The following information is courtesy of the Centers for Disease Control and Prevention. Heat cramps may be the first sign of heat-related illness, and may lead to heat exhaustion or stroke. Symptoms include painful muscle cramps and spasms, usually in the legs and abdomen, and heavy sweating. To treat cramps, apply firm pressure on cramping muscles or gently massage them to relieve spasm. Take sips of water unless nausea occurs, then stop drinking.

If a person experiences any of the following symptoms, heat exhaustion may have set in: heavy sweating; weakness; cool, pale, clammy skin; fast, weak pulse; possible muscle cramps; dizziness; nausea or vomiting; or fainting. Treatment includes laying the person down in a cooler environment, loosening clothing, applying cool, wet cloths to as much of the body as possible, fanning the body, and sips of water. If the person vomits more than once, seek immediate medical attention.

Heat stroke is the worst type of heat illness and is sometimes marked by an altered mental state. One or more of the following symptons is present: throbbing headache, confusion, nausea, dizziness, shallow breathing. Also the body temperature rises above 103°F, skin becomes hot, red, dry or moist, a rapid and strong pulse is felt, and the person faints or loses consciousness. Heat stroke is a severe medical emergency. Call 911 or get the victim to a hospital immediately. Delay can be fatal. Do not give fluids, otherwise treat the person as you would for heat exhaustion until medical assistance arrives.

For more information on heat safety, check out this detailed heat awareness webpage from the National Weather Service.  Most of the information contained in this article was originally published by NOAA/National Weather Service and NoHeatStroke.org. MemphisWeather.net is a NOAA Weather-Ready Nation Ambassador and we use their published material to help improve the nation’s readiness, responsiveness, and overall resilience against extreme weather, water, and climate events.

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