Extreme Heat & Health

Key Takeaways

  • Extreme heat is the leading cause of weather-related deaths in the United States.
  • In the future, Harris County is expected to have higher temperatures and more extreme heat days.
  • High temperatures and humidity can cause heat-related illnesses, such as heat cramps, heat exhaustion and heat stroke.
  • Certain populations, such as the elderly, young children, and those with diabetes, are at  increased risk of heat-related illnesses.
  • Reducing exposure to high outdoor temperatures and having access to air conditioning can provide relief and prevent heat-related illnesses.
  • There are ways to reduce urban heat through better urban design, the addition of trees and greenspace, and the reduction of greenhouse gas emissions.

Extreme Heat in Harris County

Hot and humid weather is typical within Harris County and Southeast Texas. According to the Climate Impact Assessment for the City of Houston, more extreme heat days, hotter nights, longer summers and higher energy demands are projected for the Greater Houston Area in the future.

When temperatures become extremely high and humidity levels peak, heat stroke, heat exhaustion, heat cramps and dehydration become a concern. Extreme heat can also exacerbate pre-existing conditions such as cardiovascular disease, asthma, chronic obstructive pulmonary disease (COPD), and diabetes.

Heat Stroke

Heat stroke occurs when the body temperature rises quickly, sweating does not occur, and the body is unable to cool down on its own. Body temperature may rise to 106°F or higher within 10-15 minutes.

Warning Signs
  • Very high temperature (>103º)
  • Nausea
  • Red, hot, dry skin
  • Confusion
  • Fast, strong pulse
  • Unconsciousness
  • Dizziness
  • Throbbing headache
What To Do
  • Move person into the shade or an air-conditioned room
  • Bring the person’s temperature down using any method available - ice packs, cool water in a tub or shower; cool water from a garden hose; or wrap the person in cool, wet sheets
  • Do not give person any fluids to drink
  • Perform CPR if needed

Heat Exhaustion

Heat exhaustion can develop after several days of exposure to high temperatures and not enough or unbalanced replacement of fluids. People at greater risk include the elderly, people with high blood pressure, and people working or exercising in a hot environment.

Warning Signs
  • Heavy sweating
  • Nausea or vomiting
  • Muscle cramps
  • Fainting
  • Weakness
  • Cool and moist skin
  • Dizziness
  • Fast and weak pulse
  • Headache
  • Fast and shallow breathing
What To Do
  • Find an air-conditioned environment and rest
  • Take a cool shower or bath
  • Drink cool, nonalcoholic beverages

Heat Cramps

Heat cramps are muscle pains or spasms - usually in the arms, legs, or abdomen. Sweating depletes the body’s salt and moisture. If you have heart disease or are on a low-sodium diet, get medical attention for heat cramps.

What To Do
  • Stop all activity and sit quietly in a cool place
  • Drink water, clear juice or a sports beverage
  • Seek medical attention for heat cramps if they do not subside in 1 hour
Who is Impacted?


Extreme Heat Vulnerability Assessment

The Extreme Heat Vulnerability Assessment is the first of several climate vulnerability assessments the Climate Program has planned. Areas with the most exposure, the highest population sensitivity, and the least ability to adapt will be identified as the highest priority for public health interventions. Flooding and Air Quality Vulnerability Assessments are planned for 2021.

This assessment combines health, economic, governmental, community, and environmental indicators together to create a vulnerability score for each census tract. The vulnerability score allows us to compare different areas to one another. The score assigned to each census tract is calculated using sixteen different indicators. The indicators are separated into three different categories: exposure, sensitivity, and adaptive capacity. A combination of these categories calculates the overall vulnerability score. For more in-depth explanation of the vulnerability assessment and calculations, please see the Methods document.

Adaptive Capacity
Heat Index*
Household air conditioning
Night-time cooling
Cardiovascular diseases
Distance to cooling center
Respiratory conditions
Tree canopy coverage
Households living below poverty line
65+ years of age
Less than 5 years of age
Limited English proficiency
Outdoor workers
Population of Color
No health insurance
People with disabilities

* Heat Index: According to the National Weather Service, the heat index is what the temperature feels like to the human body when relative humidity is combined with the air temperature.

Identifying Vulnerable Areas

The map below depicts the overall vulnerability for extreme heat and health throughout Harris County. Click on the map for an interactive look at all of the indicators. Click here to open this map in a new tab.

Additional Assessment Information

  • The Heat Vulnerability Story Map provides information about the assessment process and why we looked at certain indicators. As you progress through the story map, you will discover how the different categories come together to create this heat and health vulnerability assessment.
  • This assessment relies on various indicators from different sources with varying levels of quality. Utilize the Indicators page for an in-depth explanation of each indicator. Here you will be able to find why the indicator is important for health, references, data sources, and limitations.
  • For more details about the methods used to create the vulnerability assessment, please see the Methods document
  • This assessment will be updated as new data becomes available.
Special Thanks - Thank you to the Harris County Public Health (HCPH) Data Warehouse team, Harris County Appraisal District, National Center for Atmospheric Research (NCAR), Dr. Stephen Linder, and the Health of Houston Survey for providing their expertise and sharing valuable data with our team. This assessment would not be possible without their contributions.