Heat kills by pushing the human body beyond its limits. In extreme heat and high humidity, evaporation is slowed and the body must work extra hard to maintain a normal temperature.
Most heat disorders occur because the victim has been overexposed to heat or has over-exercised for his or her age and physical condition. Older adults, young children and those who are sick or overweight are more likely to succumb to extreme heat.
Conditions that can induce heat-related illnesses include stagnant atmospheric conditions and poor air quality. Consequently, people living in urban areas may be at greater risk from the effects of a prolonged heat wave than those living in rural areas. Also, asphalt and concrete store heat longer and gradually release heat at night, which can produce higher nighttime temperatures known as the "urban heat island effect."
A heat wave is an extended period of extreme heat, and is often accompanied by high humidity. These conditions can be dangerous and even life-threatening for humans who don't take the proper precautions.
Extremely hot temperatures can result in death, especially among the medically fragile and elderly and have significant impacts on agriculture.
• About 20 people die each year from heat-related emergencies, but a severe or extended heat wave can cause more casualties. For example, a 13-day heat wave in 2006 resulted in 136 deaths.
• Multi year droughts may result in water shortages, which impact water available for human consumption and agriculture production in the more arid areas of the state.
The California Governor's Office of Emergency Services Heat Contingency Plan describes state operations during heat related emergencies and provides guidance on the preparation of local heat emergency response plans. Steps to protect you from heat emergencies are also available below.
Terms to Know
Heat Wave: At least 3 days of abnormally high heat (90 degrees Fahrenheit or higher) and high uncomfortable humidity (80% relative humidity or higher) are expected.
Heat Index: A number in degrees Fahrenheit that tells how hot it really feels when relative humidity is added to the actual air temperature. Exposure to full sunshine can increase the heat index by 15 degrees. It is also known as the "Apparent Temperature"
Excessive Heat Watch: Heat watches are issued when conditions are favorable for an excessive heat event in the next 24 to 72 hours. A Watch is used when the risk of a heat wave has increased but its occurrence and timing is still uncertain.
Excessive Heat Warning: An Excessive Heat Warning is issued within 12 hours of the onset of extremely dangerous heat conditions. The general rule of thumb for this Warning is when the maximum heat index temperature is expected to be 105° or higher for at least 2 days and night time air temperatures will not drop below 75°.
Heat Advisory: A Heat Advisory is issued within 12 hours of the onset of extremely dangerous heat conditions. A heat advisory is issued when maximum daytime heat index values are forecast to reach 100 to 104°F for at least 2 consecutive hours.
Excessive Heat Outlooks: These are issued when the potential exists for an excessive heat event in the next 3-7 days. An Outlook provides information to those who need considerable lead-time to prepare for the event.
UV Index: A rough measure of the amount of harmful ultraviolet radiation in the sunlight reaching the Earth's surface at a given location, given the time of year and current atmospheric conditions, expressed in terms of the risks that are associated with exposure to that amount of radiation.
Heat Health Hazards
Heat Stroke: This condition is also known as sunstroke, which can be life threatening. Body temperature can rise and cause brain damage; death may result if not cooled quickly. Signals include hot, red and dry skin; changes in consciousness; rapid, weak pulse, and shallow breathing. Relief for lowering body temperature can be with a cold bath or sponge.
Heat Exhaustion: This condition is less dangerous than heat stroke. It usually occurs when people exercise too heavily or work in warm, humid places where body fluids are lost. Signals include cool, moist, pale or flushed skin; heavy sweating; headache; nausea or vomiting; dizziness and exhaustion. If symptoms occur, get the victim out of sun, and apply cool, wet cloths.
Sunburn: Redness and pain; in severe cases, swelling of skin, blisters, fever, and headaches. Sunburn slows the skin's ability to cool itself. Ointments can be a relief for pain in mild cases. A physician should see serious cases.
Heat Cramps: Heat cramps are muscular pains and spasms caused by heavy exertion. Signals are abdominal and leg muscle pain. Loss of water and salt from sweating causes cramping. Relief can be firm pressure on cramping muscles, or gentle massages to relieve cramping.
Heat Rashes: Heat rashes are a common problem resulting from persistent wetting of clothing by unevaporated sweat.
To begin preparing, you should build an emergency kit and make a family communications plan.
- Install window air conditioners snugly; insulate if necessary.
- Check air-conditioning ducts for proper insulation.
- Install temporary window reflectors (for use between windows and drapes), such as aluminum foil-covered cardboard, to reflect heat back outside.
- Weather-strip doors and sills to keep cool air in.
- Cover windows that receive morning or afternoon sun with drapes, shades, awnings, or louvers. (Outdoor awnings or louvers can reduce the heat that enters a home by up to 80 percent.)
- Keep storm windows up all year.
- Listen to local weather forecasts and stay aware of upcoming temperature changes.
- Know those in your neighborhood who are elderly, young, sick or overweight. They are more likely to become victims of excessive heat and may need help.
- Be aware that people living in urban areas may be at greater risk from the effects of a prolonged heat wave than are people living in rural areas.
- Get trained in first aid to learn how to treat heat-related emergencies.