Excessive Heat


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.

Before Extreme Heat

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.

During Extreme Heat

General Safety Tips During a High Heat Event

  • Slow down on strenuous activity and exercise, especially during the sun's peak hours: 11 AM - 4 PM. Exercise should be done in the early morning between 4 - 7 AM.
  • Never leave children or pets alone in closed vehicles.
  • Stay indoors as much as possible and limit exposure to the sun.
  • Stay on the lowest floor out of the sunshine if air conditioning is not available.
  • Postpone outdoor games and activities.
  • Consider spending the warmest part of the day in public buildings such as libraries, schools, movie theaters, shopping malls, and other community facilities. Circulating air can cool the body by increasing the perspiration rate of evaporation.
  • Eat well-balanced, light, and regular meals. Avoid using salt tablets unless directed to do so by a physician.
  • Drink plenty of water; even if you do not feel thirsty. Avoid drinks with caffeine. Consult a doctor before increasing liquid intake if you: have epilepsy; have heart, kidney, or liver disease; are on a fluid-restricted diet; or have a problem with fluid retention.
  • Limit intake of alcoholic beverages
  • Dress in loose-fitting, lightweight, and light-colored clothes that cover as much skin as possible. Avoid dark colors because they absorb the sun’s rays.
  • Protect face and head by wearing a wide-brimmed hat.
  • Check on family, friends, and neighbors who do not have air conditioning and who spend much of their time alone
  • Check on your animals frequently to ensure that they are not suffering from the heat. Go to a designated public shelter if your home loses power during periods of extreme heat. Text SHELTER + your ZIP code to 43362 (4FEMA) to find the nearest shelter in your area (example: shelter 12345).
  • Listen to NOAA Weather Radio for critical updates from the National Weather Service (NWS).


  • Never leave children in a parked car or vehicle during periods of intense summer heat. Temperatures inside a closed vehicle can reach over 140 degrees Fahrenheit quickly. Exposure to such high temperatures can kill within a matter of minutes.
  • Strenuous activities should be reduced, eliminated or rescheduled to the coolest time of the day. Make sure that children get lots of rest when they are active. Heat can make children feel tired.
  • Make sure children are well-hydrated and provide them drinking water regularly, even before they ask for it.
  • If your home does not have air-conditioning, find a nearby building that does. Libraries can be a great place for a cool retreat from the heat.
  • Infants and children up to four years of age are especially sensitive to the effects of high temperatures. They rely on others to regulate their environments and provide adequate liquids.

Senior Citizens

  • People who are 65 years of age or older may not compensate for heat stress efficiently, and are less likely to sense and respond to change in temperature.
  • Seniors don't 'feel the heat' the way younger people do, and so might not be aware of the risks of high temperatures.
  • Senior citizens can have chronic medical conditions that changes normal body responses to heat.
  • Be aware that prescription medicines can impair the body's ability to regulate its temperature or that inhibit perspiration.


  • Never leave your pet in a parked car or vehicle during periods of intense summer heat, not even for a minute. Temperatures inside a closed vehicle can reach over 140 degrees Fahrenheit quickly. Exposure to such high temperatures can kill within a matter of minutes.
  • Be aware that asphalt can get very hot and burn your pet's paws - walk pets on the grass when possible.
  • Make sure there is enough water and food for pets and limit their exercise.
  • Don't rely on a fan.  Animals respond differently to heat than humans do, and fans don't cool off pets as effectively as they do people.
  • Check on animals frequently to ensure that they are not suffering from the heat.
  • Any time your pet is outside, ensure they have water and a shady place to rest.
  • Cats and dogs can get sunburn. Cats with white ears are prone to develop sunburn on the tips and edges of the ears. Dogs that are hairless or dogs with light colored fur can develop sunburn. Dogs with pink noses are also susceptible to the effects of sunburn.

Energy Conservation

  • Power outages are more likely to occur during warm weather when utility usage is at its peak.  To avoid putting a strain on the power grid, conserve energy when possible to help prevent power disruptions.
  • Set the air conditioner thermostat no lower than 78 degrees.
  • Only use the air conditioner when home.  If you want to cool your home before you return, set a timer to have it switch on no more than a half-hour before you arrive.
  • Use portable or ceiling fans; mild air movement of 1 MPH can make the room feel 3 to 4 degrees cooler.
  • In warm weather, run ceiling fans counterclockwise so airflow under the fan will push down and create a wind-chill effect.  Running the fan in a clockwise direction creates a gentle updraft, but recirculates heat down.
  • On hot days, avoid using the oven; cook on the stove, use a microwave oven, or grill outside.
  • Turn non-essential appliances off.  Unplug appliances and electronics when not in use.
  • Plug home electronics, such as TVs, DVD players and computers into power strips and turn off the power strips when the equipment is not in use.
  • Minimize indoor heat by only using appliances that have heavy electrical loads early in the morning or very late at night.


Additional Resources