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Heat is the leading cause of weather-related deaths in the United States, which kills more people than tornadoes, floods, and hurricanes. In Nevada, the impact of climate change has led to more frequent, more severe, and longer episodes of extreme heat. For example, cities such as Reno and Las Vegas are warming up faster than any other cities in the country.1 Nevada’s warming climate increases the risk for heat-related illnesses, some of which can be serious and even deadly. However, heat-related illnesses are preventable.  

1 Earth Day: Warming & Solutions (Climate Central)  

HRI in Nevada

Heat-Related Illness

What is heat-related illness?

Heat-related illness occurs from exposure to extreme heat, preventing the body from cooling down properly. Extreme heat is when temperatures are much hotter than normal. Humidity can also influence periods of extreme heat since humid conditions can make it feel much hotter than it really is.

What are types of heat-related illness?

Heat-related illnesses vary from minor issues, such as sunburn, heat rash, and heat cramps, to more severe and potentially life-threatening conditions like heat stroke.

Heat Stroke

Heat stroke is a serious and life-threatening condition caused by overheating. This happens when the body loses its ability to regulate temperature, causing a fast rise in body temperature. With heat stroke, the body’s ability to sweat stops, preventing the body from cooling down. Heat stroke is the most serious heat-related illness, and it can cause death or permanent disability—seek immediate medical help.

Signs and Symptoms 

  • A body temperature greater than 103°F (39.4°C)
  • Hot, red, or dry skin
  • Rapid, strong pulse
  • Throbbing headache
  • Dizziness
  • Vomiting
  • Confusion, altered mental status, slurred speech
  • Unconsciousness
  • Seizures


Heat Exhaustion

Heat exhaustion is less severe than heat stroke, but if untreated, it may progress to heat stroke. Heat exhaustion happens when the body experiences significant loss of water and salt, typically due to excessive sweating.

Signs and Symptoms 

  • Muscle cramping
  • Tiredness
  • Headache
  • Vomiting
  • Dizziness
  • Heavy sweating
  • Cold, pale, and clammy skin
  • Rapid, weak pulse
  • Fainting


  • Move the person to a cooler or shaded environment
  • Have the person rest, lying down on their back
  • Immerse the person in cool water or cool shower
  • Place cool, damp cloths or ice packs on the head, neck, armpits, and groin area or soak the clothing with cool water
  • Wear lightweight clothing
  • Have the person frequently sip cool nonalcoholic beverages, prioritizing water or electrolytes drinks
  • Seek immediate medical help if the symptoms worsen or last longer than one hour

Heat Cramps

Heat cramps are painful muscle spasms in the abdomen, arms, or legs, often occurring during or after physical activity in hot conditions. Individuals who sweat a lot during intense physical activity are more likely to experience heat cramps. Low salt levels in muscles due to sweating can potentially be the cause of painful cramps.

Signs and Symptoms

  • Heavy sweating during physical activity
  • Muscle pains or spasms


  • Stop all activities and move the person to a cooler or shaded environment
  • Have the person drink water or an electrolyte beverage
  • Have the person rest and wait until cramps go away before beginning more physical activity
  • Apply firm pressure to cramped muscles or gently massage them to relieve spasm
  • Seek immediate medical help if cramps last longer than one hour, or the person is on a low-sodium diet or has heart problems


Sunburn results from overexposure to ultraviolet (UV) rays from the sun, leading to skin damage.

Signs and Symptoms

  • Painful, red, and warm skin
  • Blisters on the skin
  • Swollen Skin
  • Headache
  • Fever
  • Vomiting
  • Fatigue


  • Avoid sunlight until sunburn heals
  • Wear cool clothes on sunburned areas
  • Apply sunscreen and cover sunburned areas with sun protective clothing if going outside
  • Take baths with cool water
  • Apply moisturizing lotion to sunburned areas
  • Avoid breaking blisters
  • Seek medical help if sunburn affects infants younger than one year old or if the person is experiencing fever, blisters, or severe pain

Heat Rash

Heat rash is a skin irritation from excessive sweating in hot weather, resulting in itchy, red bumps or blisters.

Signs and Symptoms

  • Red clusters of small blisters or bumps on the skin, typically found on the neck, upper chest, groin, under breasts, or in elbow creases


  • Stay in a cool, less humid environment
  • Keep the rash dry
  • Avoid moisturizers
  • Avoid hot environments and wear loose clothing

Learn More About the Types of Heat-Related Illnesses

Click on the following links for additional information about heat-related illnesses:

Who is at increased risk for heat-related illness?

Heat-related illness can affect anyone, but some groups are at higher risk.

Infants and Children

Children’s bodies are not as good at controlling temperature as adults’ bodies. Children also rely on others to keep them cool and safe during hot weather.

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Older Adults (Aged 65+)

Older adults’ bodies do not respond as well to heat as younger individuals. Older adults are more likely to be affected by chronic medical conditions and are more likely to be taking certain prescription medicines, both of which can affect the body’s response to heat.

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Individuals with Chronic Medical Conditions

People who are affected by heart disease, mental illness, poor blood circulation, and obesity may be more at risk for heat-related illness.

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Athletes and People who Recreate Outdoors

People who participate in sports and recreational activities in extreme heat can become dehydrated and get heat-related illness.

Learn More

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Workers Exposed to Heat

People who work outdoors (e.g., farm workers, miners, construction workers, etc.) are most likely to become dehydrated and get heat-related illness. Indoor workers who work in hot environments (e.g., bakery workers, miners, boiler room workers, etc.) can also be at risk.

Learn More

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Low-Income Households

People who live in homes without air conditioning can be at higher risk of heat-related illness during an extreme heat event.

Learn More

Click on the following links for additional information about low-income households and heat:

Unhoused Persons

People who are unhoused often lack access to clean drinking water, air conditioning, or transportation to cooling centers, which places them at risk of heat-related illness and even death.

Learn More

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Pregnant Persons

Pregnant persons’ bodies must work harder to cool down both their body and the developing baby. This makes pregnant people more likely to get heat-related illness than nonpregnant people.

Learn More

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Learn More About Risk Factors

Click on the following link for additional information about risk factors for heat-related illness:

How do I prevent heat-related illness?

Heat-related illness is preventable. However, brief exposure to high temperatures can lead to severe and potentially life-threatening health issues. Consult your doctor about how heat might impact chronic conditions or medications. The following precautions can help you prevent heat-related illness.

Stay Cool

  • Wear lightweight, light-colored, and loose-fitting clothing
  • Stay in an air-conditioned place, such as a shopping mall or public library, or call your local health department about cooling centers in your area
  • Perform outdoor activities when it is coolest, such as mornings and evenings
  • Reduce exercise during heat
  • Wear sunscreen with an SPF of 15 or higher that says “broad spectrum” or “UVA/UVB protection” 30 minutes prior to going outside
  • Do not leave infants, children, or pets, in a parked car, even if the windows are cracked open

Stay Hydrated

  • Drink plenty of fluids; do not wait until you are thirsty!
  • If your doctor limits the amount you drink or has you on water pills, ask how much you should drink during hot weather
  • Avoid sugary, caffeinated, and alcoholic drinks
  • Ensure pets have plenty of fresh, cool water, and shelter from the sun

Stay Informed

  • Check your local news for extreme heat alerts and safety tips
  • Learn the signs and symptoms of heat-related illnesses and how to treat them (see What are Types of Heat-Related Illnesses? section above)
  • Know who is most at risk (see Who is at Increased Risk for Heat-Related Illnesses? section above)
  • Visit or check in with adults at greater risk of heat-related illness twice a day; infants and children need more frequent watching

Learn More About Heat-Related Illness Prevention

Click on the following links for additional information about preventing heat-related illness:

Additional Resources
Glossary of Terms

Definitions were adopted from the National Oceanic and Atmospheric Administration’s (NOAA’s) National Weather Service glossary.

Excessive Heat

Excessive heat occurs from a combination of high temperatures (significantly above normal) and high humidities. At certain levels, the human body cannot maintain proper internal temperatures and may experience heat stroke. The “Heat Index” is a measure of the effect of the combined elements on the body.

Excessive Heat Outlook

This climate prediction center (CPC) product, a combination of temperature and humidity over a certain number of days, is designed to provide an indication of areas of the country where people and animals may need to take precautions against the heat during May to November.

Excessive Heat Warning

Issued within 12 hours of the onset of the following criteria: heat index of at least 105°F for more than 3 hours per day for 2 consecutive days, or heat index more than 115°F for any period of time.

Excessive Heat Watch

Issued by the National Weather Service when heat indices in excess of 105ºF (41ºC) during the day combined with nighttime low temperatures of 80ºF (27ºC) or higher are forecast to occur for two consecutive days.

Heat Advisory

Issued within 12 hours of the onset of the following conditions: heat index of at least 105°F but less than 115°F for less than 3 hours per day, or nighttime lows above 80°F for 2 consecutive days.

Heat Exhaustion

A mild form of heat stroke, characterized by faintness, dizziness, and heavy sweating.

Heat Index

The Heat Index (HI) or the “Apparent Temperature” is an accurate measure of how hot it really feels when the Relative Humidity (RH) is added to the actual air temperature.

Heat Stroke

A condition resulting from excessive exposure to intense heat, characterized by high fever, collapse, and sometimes convulsions or coma.

Heat Wave

A period of abnormally and uncomfortably hot and unusually humid weather. Typically, a heat wave lasts two or more days.

Urban Heat Island

The increased air temperatures in urban areas in contrast to cooler surrounding rural areas.

HRI Data

Nevada Heat-Related Illness Dashboard

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