Excessive Heat

thermometer and sun graphic

Heat related deaths and illnesses are preventable, yet heat is one of the leading weather-related kilers in the U.S.1 From May-September 2021, there were 1,543 deaths due to heat-related illnesses in the United States, with provisional mortality estimates indicating even greater numbers of death in 2022 and 2023.2 

Excessive heat is defined as temperatures that are much hotter and/or humid than average for a particular location and the time of year. Excessive heat events are becoming more frequent, due to the warming of our planet. Prolonged hot weather can cause dehydration and increase the body’s core temperature, making it difficult for the body to function normally.

What Causes Heat Related Illness?

Heat illness occurs when the body cannot cool down. The body normally cools itself by sweating, however, sometimes that is not enough. In excessive heat, especially when humidity is high, sweat does not evaporate as quickly and the body has to work extra hard to maintain its normal temperature. Other factors can also contribute to how our body regulates temperature, such as age, health conditions, and medication or drug use.

There are several types of heat related illness: heat rash, heat cramps, heat exhaustion, and heat stroke. See Table 1 for types of heat related illnesses and their symptoms. The most serious form of heat related illness is heat stroke. This occurs when the body’s temperature rises quickly, the sweating mechanism fails, and the body cannot cool down. If not addressed on time, heat stroke can cause permanent damage or can lead to death.

[1] National Weather Service, National Oceanic and Atmospheric Administration. Heat Safety Tips and Resources. https://www.weather.gov/safety/heat

[2] Centers for Disease Control and Prevention, National Center for Health Statistics. National Vital Statistics System, Provisional Mortality on CDC WONDER Online Database. Accessed at http://wonder.cdc.gov/mcd-icd10-provisional.html

Who is At Risk?

  • Elderly (65+)
  • Babies and young children
  • People with pre-existing or chronic conditions, such as diabetes, high blood pressure, heart disease, mental illness, developmental disability, dementia, respiratory conditions, asthma, and obesity
  • The unsheltered/homeless
  • Outdoor workers and athletes
  • People without air conditioning
  • People living alone and socially isolated
  • People taking diuretics, such as caffeine and alcohol or illegal drugs
  • Your pets

How to Take Care of Myself?

  • Stay somewhere cool or get to one of the County’s Cool Zones
  • Take a cold shower or bath
  • Stay hydrated and drink plenty of water
  • Avoid drinks that contain alcohol, caffeine, and lots of sugar
  • Wear light clothing and hats
  • Avoid being outdoors during hottest part of the day (10am-4pm)
  • Avoid strenuous activity
  • Do not leave children in cars on hot days
  • Do not leave pets in cars

How to Help Others?

  • Check in on neighbors, family, or friends who are at increased risk, especially if they live alone
  • Ensure they have access to plenty of water, ice in their freezer, and a fan if possible
  • Offer to help them get to a cool zone or another cool location

What is the County’s Response?

In an excessive heat event, the Public Health Services branch of the County of San Diego Health and Human Services Agency is responsible for coordinating response efforts with other County departments and external partners.

For more information, see the consumer version of the Excessive Heat Response Plan.

TABLE 1. HEAT RELATED ILLNESSES

HEAT RASH
WHAT TO LOOK FOR WHAT TO DO
  • Looks like a cluster of red pimples
  • Commonly occurs on the neck and upper chest, in the groin, under the breasts, and in elbow creases
  • Stay in a cool, dry place
  • Keep the rash dry
  • Soothe rash with powder, such as baby powder
HEAT CRAMPS
WHAT TO LOOK FOR WHAT TO DO
  • Muscle pains or spasms usually occurring in the abdomen, arms, or legs commonly a result of strenuous activity
  • Stop physical activity and move to a cool place
  • Drink water or sports drink
  • Wait for cramps to go away before doing more physical activity
  • Get medical help if:
    • Cramps last more than 1 hour
    • You are on a low sodium diet
    • You have heart problems
HEAT EXHAUSTION
WHAT TO LOOK FOR WHAT TO DO
  • Paleness
  • Dizziness
  • Headache
  • Tiredness
  • Weakness
  • Muscle cramps
  • Excessive sweating
  • Nausea or vomiting
  • Fainting
  • Move to a cool place
  • Loosen your clothes
  • Put cool, wet clothes on your body or take a cool bath
  • Sip water
  • Get medical help right away if:
    • You are throwing up
    • Your symptoms get worse
    • Your symptoms last longer than 1 hour
HEAT STROKE
WHAT TO LOOK FOR WHAT TO DO
  • Extremely high body temperature (103⁰F or higher)
  • Dizziness
  • Throbbing headache
  • Nausea or vomiting
  • Difficulty breathing
  • Mental confusion, delirium, or hallucinations
  • Red, hot, dry skin
  • Chills
  • Rapid, strong pulse
  • Unconsciousness
  • CALL 911 RIGHT AWAY -- HEAT STROKE IS A MEDICAL EMERGENCY
  • Move the person to a cooler place
  • Help lower the person's temperature with cool cloths or a cool bath
  • Do not give the person anything to drink
Source: Centers for Disease Control and Prevention
Excessive Heat Report

2023 Annual Excessive Heat Report

The 2023 Annual Excessive Heat Report details the number of Heat Alerts and heat events year-to-year, prehospital data and outcomes, medical encounter and death data, Aging and Independence Services (AIS) activities, including Cool Zone coordination, electric fan distribution, and collaborations with the Epidemiology and Immunization Services Branch, 2-1-1 San Diego activities, and the outreach efforts that the County Communications Office (CCO) completed.

 

View the Excessive Heat Report. 

Additional Resources

Extreme Heat, CDC and Prevention

Extreme Heat, Ready.gov

Extreme Heat, CDPH

Extreme Heat, USEPA

Killer Heat, Union of Concerned Scientists

Heat Safety, National Weather Service

Heat Index, National Weather Service