Hazards: Extreme Heat

Extreme Heat icon

Extreme heat and high humidity can be deadly, slowling evaporation and requiring the body to work harder just to maintain a comfortable temperature.

Overexposure to heat or overextertion (too much exercise or effort) can trigger a heat disorder. Children, older adults, those who are sick or overweight are all at heightened risk.

Take the proper precautions to keep you, your family and your pets safe.


sun iconGeneral Summer safety tips are also available, covering fireworks, grilling, pool safety and more.

What to Do

To keep cool during extreme heat, Fairfax County encourages residents to follow this general advice:

  • Never leave children or pets alone in a closed vehicle.
  • Drink plenty of fluids: Drink two to four glasses of cool fluids each hour.
    • Your body needs water to keep cool. Drink water even if you don't feel thirsty.
    • Do not drink caffeinated or alcoholic beverages because they dehydrate the body.
  • Keep cool indoors: If you can, stay in an air-conditioned area.
    • Ensure your home's cooling system is working properly before it is truly needed. 
    • Resting for just two hours in air conditioning can significantly reduce heat-related illnesses.
    • Consider spending the warmest part of the day in public buildings such as libraries, schools, movie theathers, shopping malls and other community facilities.
    • Electric fans may provide comfort, but with temperatures in the 90s, fans will not prevent heat-related illness.
  • Avoid strenuous physical activities or reschedule outdoor activities for the coolest part of the day, usually the early morning. Limit physical activity until your body adjusts to the heat.
  • Wear sunscreen to prevent sunburn. Sunburn makes it more difficult for your body to cool off.
    • Wear light-colored clothing, which helps reflect sunlight.
  • Eat light meals, avoiding high-protein foods because they increase metabolic heat.
  • Don’t take salt tablets unless directed by a physician.

Cooling Centers

Fairfax County Cooling Centers in a larger map

During extremely hot days, there is plenty residents can do to stay cool; resting for just two hours in air conditioning can significantly reduce heat-related illnesses. Residents can take in a movie, stroll through a shopping center or visit one of the Fairfax County Cooling Centers

Residents are encouraged to check the operating hours to ensure the facility is open before arriving.

Helping the Vulnerable Through Extreme Heat

The needs of Fairfax County’s vulnerable populations, including the homeless, older adults and those with special medical needs, are heightened during conditions such as extreme heat.

Residents who know individuals needing special attention are encouraged to check in on them to ensure their well-being. If residents need immediate, life-saving help, call 9-1-1. For other safety help, call the public safety non-emergency phone number at 703-691-2131, TTY 711.

Heat takes the greatest toll on the very young and the very old, especially children younger than 5 and those older than 65. Intense summer temperatures also greatly affect people who are already sick or take certain medications, including diuretics, antihistamines, beta-blockers and tranquilizers.

Fairfax County residents who need help to keep their homes cool this summer and prevent a health emergency resulting from extreme heat, may be able to get assistance from two programs locally administered by the county:

Residents who need immediate help with utility bills or other urgent human services assistance can call the county’s Coordinated Services Planning staff at 703-222-0880, TTY 703-803-7914. County staff can connect residents with a network of services provided by public, private and community-based organizations, as well as appropriate county government resources.

Keep Pets Cool

Fairfax County Animal Control Officers respond to dozens of reports of animals locked in hot cars in parking lots each summer and urge pet owners to keep pets at home on hot days.

Pet owners are urged to remember the following tips:

  • Never leave pets in a parked car. On a warm day, temperatures can rapidly rise to dangerous levels. If you see an animal in distress in a parked car, contact police. Even with the windows slightly open, the temperature in a car on a 93-degree day can soar to 125 degrees in just 20 minutes and approximately 140 degrees in 40 minutes.
  • Shade and water are vital to pets. Pet owners must provide adequate shelter protecting animals from injury, rain, sleet, snow, hail, direct sunlight, and adverse effects of heat or cold. A dog house in the backyard with no access to shade does not protect animals from sun.
  • Limit exercise on hot days. Take care to adjust intensity and duration of exercise. Watch for shortness of breath and remember that asphalt gets very hot and can burn paws; walk your dog on the grass if possible.
  • Know the signs of pet illness. If your pet shows any of the following signs contact your veterinarian or animal hospital immediately:
    • heavy panting
    • glazed eyes
    • rapid heartbeat
    • vomiting
    • fever
    • dizziness
    • restlessness
    • excessive thirst
    • profuse salivation

Take steps to reduce the animal’s body temperature; apply ice packs or cold towels to the head, neck and chest, provide water and ice cubes for hydration, and move the animal into the shade or air-conditioning. 

Extreme Heat Terms

Heat Wave
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 without proper precautions.

Heat Index
The heat index is the temperature the body feels when the effects of heat and humidity are combined. Exposure to direct sunlight can increase the heat index by as much as 15° F.

Heat Advisory
Heat Index values are forecast to meet locally defined advisory criteria for 1 to 2 days (daytime highs=100-105° Fahrenheit).

Excessive Heat Watch
Conditions are favorable for an excessive heat event to meet or exceed local Excessive Heat Warning criteria in the next 24 to 72 hours.

Excessive Heat Warning
Heat Index values are forecast to meet or exceed locally defined warning criteria for at least 2 days (daytime highs=105-110° Fahrenheit).

Related Information

Contact Fairfax County: Phone, Email or Twitter | Main Address: 12000 Government Center Parkway, Fairfax, VA 22035
Technical Questions: Web Administrator

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