A heat wave is an abnormal weather event that lasts at least two days, bringing above average temperatures to a particular region. A heat wave occurs when a high-pressure system traps warm air over a region, forming a dome of hot air that doesn’t circulate or cool down. 

Heat waves aren’t a typical natural disaster, like a tornado or flood. But they can be extremely dangerous for people and pets. Staying outdoors for long periods of time can cause heat exhaustion or heat stroke. Often, high humidity can make outdoor air temperatures even more dangerous, as your body has a harder time cooling off.  According to the Environmental Protection Agency, more than 1,000 people die every year from exposure to extreme heat. 

During a heat wave you should try and limit physical activity outdoors to reduce your chances of heat stroke or exhaustion. Try to wear lightweight, light-colored clothing, and drink plenty of water. Lastly, remember to wear sunscreen and limit sun exposure to avoid sunburns. (Source: NOAA)

What to look for

Excessive Heat Warning: Issued within 12 hours of the onset of extremely dangerous heat conditions. The general rule of thumb, according to NOAA, is when the maximum heat index temperature is expected to be 105° or higher for at least two days and night time air temperatures will not drop below 75°.

Excessive Heat Watch: Heat watches are issued when conditions are favorable for an excessive heat event in 24 to 72 hours.

Heat Advisory: An advisory is issued within 12 hours of the onset of “extremely dangerous heat conditions,” according to NOAA. The general rule of thumb for this is when the maximum heat index temperature is expected to be 100° or higher for at least two days, and night time air temperatures will not drop below 75°. However, this varies, so take precautions.

Excessive Heat Outlooks: Outlooks are issued when the potential exists for an excessive heat event in the next three to seven days.

(Source: NOAA)

Health impacts of intense heat

Heat cramps: This is the mildest reaction you might have to heat exposure, usually after strenuous activity in extreme heat. Your body’s moisture and salt levels may become depleted, causing muscle cramps. If you feel cramps, it’s important to get rest, drink plenty of water and eat snacks that are heavy in carbohydrates. 

Heat exhaustion: If you don’t recognize and treat the signs of heat exhaustion, it may lead to heatstroke, which can be fatal. Signs of heat exhaustion include goose bumps on the skin, heavy sweating, or feeling faint, dizzy or fatigued. You may feel muscle cramps and nausea as well. If you are experiencing heat exhaustion, it’s important to get out of the heat and sun and rest. Drink water or a sports drink to stay hydrated. If your symptoms do not start to get better after rest, you may need to seek immediate medical attention. 

Heatstroke, hyperthermia: This is the most extreme response you may experience due to heat exposure. Your body temperature may rise to dangerous levels, above 104 degrees and you will likely need immediate medical attention. 

Symptoms may include nausea, confusion and slurred speech, rapid breathing and racing heart beat, and headaches. Dehydration can also begin to occur. These symptoms should be treated as soon as possible: Try to get out of the heat, whether that’s indoors or in shade. Remove excess clothing and cool down body temperatures with cold water, ice packs or wet towels on the head and neck. (Source: Mayo Clinic, NWS)

Other sources: NOAA, CDC

Heat index

A heat index indicates what outdoor air temperature “feels like” to the human body, due to humidity. When you sweat, your body cools down as water evaporates off of you. But in high humidity, your sweat doesn’t evaporate as easily and your body can’t cool off. That’s why you feel hotter in higher humidity climates, and cooler in more arid climates– even if the temperature reading from a thermometer is the same. 

In high humidity climates, it’s important to try and limit physical activity outdoors, and remember to take breaks inside with air conditioning and to drink plenty of water. 

(Source: NWS)

Risk factors

Some individuals may face higher risk of heat related illness or death than others. During heat waves, it’s crucial to check on neighbors and family members who may be vulnerable: 

  • People who are not acclimatized to high heat—for example, someone who’s never lived in a warm climate—may have a harder time adjusting to the heat and may not know their physical limits. 
  • Elderly people and infants, as their bodies may not be able to regulate temperature. 
  • Taking certain medications, such as antipsychotics, may also increase your risk of heat illness. 
  • Unhoused people, low income households, or any household without access to air conditioning all face high risks as well, since A/C provides the safest way to cool down. 

(Source: NIH)

How to prepare for blackouts and brownouts

Power outages can occur during heat waves, as energy demand to run cooling system peaks. Boil water notices may also be issued if water treatment facilities do not have power.

Utility companies and grid operators may put out alerts and warnings for potential power outages.

A brownout, or rolling outage, may be implemented first if the supply of electricity is running low on a grid. Your power may go in and out for several hours, and typically outages rotate between different areas of a city or county.

A blackout is more severe, and occurs when there is a total loss of power. Hospitals, fire stations, and water treatment plants may be able to draw power from the grid or generators.

Both types of outages can be dangerous if your home gets too hot, or if you lose access to clean running water. Particularly for people with vulnerabilities, power outages can be uncomfortable or even dangerous.

Try to put together an emergency supply kit with the following items:

  • Bottled water (recommended 1 gallon per day per person)
  • Ice and cooler to store perishable food, medicine, etc.
  • Canned foods and can opener
  • Flashlights, batteries
  • Sunscreen, hat and lightweight clothing
  • Backup chargers/batteries for phones and electronic devices
  • List of emergency contacts
  • Masks and hand sanitizer, if you need to go to a public cooling shelter

(Source: NWS)

You can also follow these tips to help conserve energy and reduce heat gain in your house:

  • Prior to the start of summer, weatherstrip doors and windows
  • Keep blinds and curtains closed to help keep rooms cooler
  • Turn your ceiling fans on to help reduce your need for AC usage
  • Try not to run large appliances, like ovens or laundry machines, during the day time.

(Source: Space City Weather)

More resources:

Air conditioning

Access to air conditioning is one of the biggest factors of your safety during a heat wave. Even a few hours in A/C has the potential to lessen your risk of heat related illness. 

If you do not have access to air conditioning during a heat wave, public spaces may be available for you to cool off. Libraries are typically always open for the general public. Recreation centers, senior centers and community centers are also usually open as cooling shelters; other spaces such as cultural centers, museums, or schools may open on a case by case basis. Some cities may also provide free public transit for people who need to access these public spaces. Check your city or county’s social media page or website for updates on these programs, as they will vary by location. 

Other public spaces like air-conditioned malls may also be accessible to the public, but they may not be officially designated as cooling centers by the city or county government. That means you might not be able to stay in that space indefinitely as it’s a private property. Source: CDC

Energy bill assistance

During a heat wave, low income households may worry about extremely high energy bills due to running an  air conditioner. There are several programs that may be able to help you offset the increased energy costs you may experience, without having to sacrifice safety. 

Every state receives federal funding through the Low Income Home Energy Assistance Program (LIHEAP) to help households afford high energy bills. Income eligibility varies based on the size of your household. You can check the income requirements here; people who receive benefits such as SNAP may be automatically eligible for assistance. 

You may need to apply for assistance through a local agency in your city or county. The information below will help you find those groups in your state.

Texas: Department of Housing and Community Affairs

Louisiana: Housing Corporation 

Mississippi: Department of Human Services

Alabama: Department of Economic and Community Affairs

Georgia: Department of Human Services

Florida: Department of Economic Opportunity 

Tennessee: Community Action Associations 

Arkansas: Department of Energy and Environment 

Kentucky: Cabinet for Health and Family Services 

West Virginia: Department of Health and Human Resources

North Carolina: Department of Health and Human Services

South Carolina: Office of Economic Opportunity 

Virginia: Department of Social Services