Extreme Heat

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Extreme Heat

Extreme heat or heat waves are among the most dangerous natural hazards. In the U.S., extreme heat kills more people than all other natural hazards and extreme weather events. Summer heat waves have been the biggest weather-related killers in Wisconsin for more than 50 years, far exceeding tornado and other storm-related deaths. Thousands of Wisconsinites fall ill or are hospitalized for heat-related illnesses each year. 

Terms Used During Extreme Heat

Excessive Heat Outlook

Used when the potential for excessive heat exists in the next three to seven days. It provides information to those who need more lead time to prepare.

Excessive Heat Warning

This is issued within 12 hours of the onset of extremely dangerous heat conditions. It will be issued by the National Weather Service when the daytime heat index is 105 or higher during the day and 75 or higher at night for at least a 48-hour period. If heat indices are 100 to 104 for four consecutive days, an excessive heat warning will be issued.

Heat Advisory

This is issued within 12 hours of the start of extremely dangerous heat conditions. The National Weather Service will issue a heat advisory for Wisconsin when the daytime heat index values are 100 to 104. A heat advisory will also be issued if heat indices are 95 to 99 for four consecutive days.

Heat Index

A measure indicating what the temperature feels like to the human body. It is when relative humidity is combined with the air temperature.

Heat Watch

This is issued when conditions are favorable for excessive heat in the next 24 -72 hours.

How Heat Index Affects You

80° - 90°F Heat Index

Fatigue is possible with prolonged exposure and/or physical activity.

90° - 103°F Heat Index

Heat stroke, cramps, or exhaustion are possible with prolonged exposure and/or physical activity.

103° - 124°F Heat Index

Heat cramps or exhaustion are likely, and heat stroke is possible with prolonged exposure and/or physical activity. 

125°F or Higher Heat Index

Heat stroke is highly likely. 

Heat-Related Illnesses

Heat related illnesses are preventable, learn the symptoms and what to do.

Heat Stroke

What to look for:

  • High body temperature (103°F or higher)
  • Hot, ready, dry, or damp skin
  • Fast, strong pulse
  • Headache
  • Nausea
  • Confusion
  • Losing consciousness (passing out)

What to do:

  • Call 911 right away
  • 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

Heat Exhaustion

What to look for:

  • Heavy sweating
  • Cold, pale, and clammy skin
  • Fast, weak pulse
  • Nausea or vomiting
  • Muscle cramps
  • Tiredness or weakness
  • Dizziness
  • Headaches
  • Fainting

What to do:

  • Move to a cool place
  • Loosen your clothes
  • Put cool, wet clothes on your body or take a cool bath
  • Sip water

Heat Cramps

What to look for:

  • Heavy sweating during intense exercise or strenuous activity
  • Muscle pain or spasms

What to do:

  • Stop physical activity and move to a cool place
  • Drink water or a sports drink

Sunburn

What to look for:

  • Painful, red, and warm skin
  • Blisters on skin

What to do:

  • Stay out of the sun until sunburn heals
  • Put cool cloths on sunburns or take a cool bath
  • Put moisturizing lotion on sunburned areas
  • Do not break blisters

Heat Rash

What to look for:

  • Red clusters of small blisters that look like pimples (usually on the neck, chest, groin, or in elbow creases)

What to do:

  • Stay in a cool, dry place
  • Keep the rash dry
  • Use powder (like baby power) to soothe the rash

Populations Vulnerable to Heat

Adults Over 65

They are less adaptable to extreme heat.

People Living Alone and/or Without Air Conditioning

They may not know when to call for help. 

Individuals With Disabilities

They are less aware and adaptable to extreme heat.

Children Under 5

Sensitive to the effects of extreme heat and rely on others to keep them cool and hydrated.

People With Chronic Medical Conditions

Medical conditions can worsen the impact of extreme heat. 

Homeless

May be unaware of cooling centers and may have limited access to other cooling methods, such as cool showers. 

Pets

Depend on their owner for adequate protection from the heat. 

Outdoor Workers

More likely to become dehydrated and more likely to get heat-related illnesses. 

Non-English Speakers

May not have access to current information about heat advisories and health risks associated with extreme heat. 

WHAT TO DO BEFORE AND DURING EXTREME HEAT

  • Do not rely on a fan as your primary cooling device. Fans create airflow but do not reduce body temperatures or prevent heat-related illnesses.
  • Identify places in your community to get cool, such as libraries, shopping malls, or contact your local health department to find a cooling center in your area. 
  • Cover windows with drapes or shades.
  • Weather-strip doors and windows.
  • Use window reflectors specifically designed to reflect heat back outside. 
  • Use a powered attic ventilator or attic fan to clear out hot air in the attic.
  • Install window air conditioners and insulate around them.
  • If you are unable to afford cooling costs, weatherization, or energy-related home repairs, visit the Wisconsin Home Energy Assistance Program (WHEAP). 

  • Take care of your body
    • Drink plenty of water. Make sure you drink before feeling thirsty. By the time you feel thirsty, you are already behind in fluid replacement. When working in the heat, drink one cup (8 ounces) of water every 15-20 minutes.
    • Limit alcohol consumption. Drinking beer and alcoholic beverages causes further body degradation.
    • It is not recommended to take salt tablets. In most cases, salt can be replaced by eating normal meals and snacks throughout the day. Do not skip meals. 
  • Cover windows to keep the sun from shining in.
  • If you have an air conditioner, use it. If you do not have one and the temperature is above 95 °F, you should go to a location where you can get cool, like a library or community center.
  • Pace yourself. Cut down on exercise during the heat. If you are not accustomed to working or exercising in a hot environment, start slowly and pick up the pace gradually. If exertion in the heat makes your heart pound and leaves you gasping for breath, STOP all activity. Get into a cool area or shade and rest.
  • Wear sunscreen. Sunburn affects your body’s ability to cool down. Put on a sunscreen of SPF 15 or higher 30 minutes before going outside and reapply as the package directs. Consider a wide-brimmed hat and sunglasses as well.
  • Consider pet and livestock safety.
    • Keep pets hydrated by providing clean and cool drinking water.
    • Provide shade with good airflow.
    • Protect their paws. Place the back of your hand on the ground for five seconds. If it’s too hot for your skin, it’s too hot for your pet’s paw pads. Consider walking your pet in the early morning or in the evening when the asphalt has cooled down.
    • Do not leave them in a car. Even with the windows cracked, the interior temperature can become deadly in minutes.
  • Check on others.
    • Check on older, sick, or frail people who may need help responding to heat.
  • Don't leave electronic equipment in hot cars.

Additional Resources

American Red Cross - Extreme Heat Safety

Ready Wisconsin - Extreme Heat

National Weather Service (NWS) - Heat Safety Tips & Resources

United States Environmental Protection Agency (EPA) - Extreme Heat

Wisconsin Department of Health Services (WIDHS) - Heat Health & Safety Tips

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