Heat is the number one weather-related killer in the United States. NOAA National Weather Service statistical data shows that heat causes more fatalities per year than floods, lightning, tornadoes, and hurricanes combined. Based on the 10-year average from 1994 to 2003, excessive heat claimed 237 lives each year. By contrast, floods killed 84; tornadoes, 58; lightning, 63; and hurricanes, 18.
In the disastrous heat wave of 1980, more than 1,250 people died. In the heat wave of 1995 more than 700 deaths in the Chicago, Illinois area were attributed to this event, and in August 2003, a record heat wave in Europe claimed an estimated 50,000 lives.
North American summers are hot; most summers see heat waves in one section or another of the United States. East of the Rockies, they tend to combine both high temperature and high humidity although some of the worst have been catastrophically dry. Additional detail on how heat impacts the human body is provided under "The Hazards of Excessive Heat" heading.
NOAA's Watch, Warning, and Advisory Products for Extreme Heat
Excessive Heat Outlook: when the potential exists for an excessive heat event in the next 3 to 7 days. An outlook is used to indicate that a heat event may develop. It is intended to provide information to those who need considerable lead time to prepare for the event, such as public utilities, emergency management and public health officials.
Excessive Heat Watch: when conditions are favorable for an excessive heat event in the next 12 to 48 hours. A watch is used when the risk of a heat wave has increased, but its occurrence and timing is still uncertain. It is intended to provide enough lead time so those who need to set their plans in motion can do so, such as established individual city excessive heat event mitigation plans.
Excessive Heat Warning/Advisory: when an excessive heat event is expected in the next 36 hours. These products are issued when an excessive heat event is occurring, is imminent, or has a very high probability of occurrence. The warning is used for conditions posing a threat to life or property. An advisory is for less serious conditions that cause significant discomfort or inconvenience and, if caution is not taken, could lead to a threat to life and/or property.
NOAA's heat alert procedures are based mainly on Heat Index Values. The "Heat Index", sometimes referred to as the "apparent temperature" and given in degrees Fahrenheit, is a measure of how hot it really feels when relative humidity is added to the actual air temperature.
To find the heat index, look at the Heat Index Chart. As an example, if the air
IMPORTANT: 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. Also, STRONG WINDS, PARTICULARLY WITH VERY HOT, DRY AIR, CAN BE EXTREMELY HAZARDOUS.
Note on the Heat Index Chart shaded zone above 105°F. This corresponds to a level that may cause increasingly severe heat disorders with continued exposure and/or physical activity.
Too Much Heat
Heat disorders generally have to do with a reduction or collapse of the body's ability to shed heat by circulatory changes and sweating, or a chemical (salt) imbalance caused by too much sweating. When heat gain exceeds the level the body can remove, or when the body cannot compensate for fluids and salt lost through perspiration, the temperature of the body's inner core begins to rise and heat-related illness may develop.
Ranging in severity, heat disorders share one common feature: the individual has overexposed or over exercised for his age and physical condition in the existing thermal environment.
Sunburn, with its ultraviolet radiation burns, can significantly retard the skin's ability to shed excess heat. Studies indicate that, other things being equal, the severity of heat disorders tend to increase with age--heat cramps in a 17-year-old may be heat exhaustion in someone 40, and heat stroke in a person over 60.
Acclimatization has to do with adjusting sweat-salt concentrations, among other things. The idea is to lose enough water to regulate body temperature, with the least possible chemical disturbance.
BEAT THE HEAT...
CHECK THE BACK SEAT!
Children, Adults, and Pets Enclosed in Parked Vehicles Are at Great Risk
Each year children die from hyperthermia as a result of being left enclosed in parked vehicles. Hyperthermia is an acute condition that occurs when the body absorbs more heat than it can dissipate. This can occur even on a mild day. Studies have shown that the temperature inside a parked vehicle can rise rapidly to a dangerous level for children, adults, and pets. Leaving the windows slightly open does not significantly decrease the heating rate. The effects can be more severe on children because their bodies warm at a faster rate than adults.
Hyperthermia deaths aren't confined to the summer months only. They also happen during the spring and fall. Below are some examples.
Adults are also susceptible to hyperthermia. On July 12, 2001 a man died of heatstroke after falling asleep in his car with the windows rolled up in the parking lot of a supermarket in Hinds County, Mississippi.
The atmosphere and the windows of a car are relatively “transparent” to the sun’s shortwave radiation (yellow in figure below) and are warmed little. However this shortwave energy does heat objects that it strikes. For example, a dark dashboard or seat can easily reach temperatures in the range of 180 to over 200 degrees F.
These objects (e.g., dashboard, steering wheel, childseat) heat the adjacent air by conduction and convection and also give off longwave radiation (red) which is very efficient at warming the air trapped inside a vehicle.
Objects Heated by the Sun Warm Vehicle's Air
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Child Safety Tips
Heat Wave Safety Tips
SUNBURN: Redness and pain. In severe cases swelling of skin, blisters, fever, headaches. First Aid: Ointments for mild cases if blisters appear and do not break. If breaking occurs, apply dry sterile dressing. Serious, extensive cases should be seen by physician.
HEAT STROKE (sunstroke): High body temperature (106° F or higher). Hot dry skin. Rapid and strong pulse. Possible unconsciousness. First Aid: HEAT STROKE IS A SEVERE MEDICAL EMERGENCY. SUMMON EMERGENCY MEDICAL ASSISTANCE OR GET THE VICTIM TO A HOSPITAL IMMEDIATELY. DELAY CAN BE FATAL. Move the victim to a cooler environment Reduce body temperature with cold bath or sponging. Use extreme caution. Remove clothing, use fans and air conditioners. If temperature rises again, repeat process. Do not give fluids. Persons on salt restrictive diets should consult a physician before increasing their salt intake.
*For more information contact your local American Red Cross Chapter. Ask to enroll in a first aid course.
Community Guidance: Preparing for and Responding to Excessive Heat Events
The "Excessive Heat Events Guidebook" was developed by the Environmental Protection Agency (EPA) in 2006, in collaboration with NOAA's National Weather Service (NWS), the Centers for Disease Control and Prevention (CDC), and the U.S. Department of Homeland Security (DHS). This guidebook provides best practices that have been employed to save lives during heat waves in different urban areas, and provides a menu of options that communities can use in developing their own mitigation plans.
Produced as a cooperative effort of NOAA's National Weather Service, the Federal Emergency Management Agency, and the American Red Cross.