National Weather Service United States Department of Commerce

Wisconsin Tornado and Severe Weather Awareness

Heat Waves

Extreme heat is the number one weather-related killer

Extreme heat and humidity is one of the leading weather-related killers in the United States, resulting in hundreds of fatalities each year.  In the disastrous heat wave of 1980, more than 1,250 people died.  In the heat wave of 1995, more than 700 deaths in the Chicago area were attributed to heat, making this the deadliest weather event in Chicago history.  In August 2003, a record heat wave in Europe claimed an estimated 50,000 lives.  

Although mostly known for its cold and snowy winters, the Badger State is not immune from the tragedies caused by heat waves.  On average, about 5 people die each summer when heat was the primary cause of death.

Recalling 1995 again, two major heat waves affected Wisconsin.  That summer in Wisconsin, 145 people died of prolonged exposure to heat and humidity along with approximately 400 heat-related illnesses.  The 1995 summer heat waves hold the record as the number one weather-related killer in Wisconsin since it became a state in 1848.  Most deaths occurred in the major urban cities in southeast Wisconsin.  The elderly and very young were hit the hardest.

For more information about heat waves, check out the National Weather Service site on heat waves!

With these tragic death tolls, the National Weather Service (NWS) has found ways to effectively warn the public of the combined dangers of heat and humidity associated with heat waves.  The NWS uses the Heat Index (HI) as an estimate of how hot it really feels when the relative humidity is added to the actual air temperature.  Click here for the HI Chart

- Heat Advisories and Excessive Heat Warnings -

The NWS will issue a heat advisory for Wisconsin when it expects the daytime heat index values to be 100 to 104.  Additionally, if heat indices will be 95 to 99 for 4 consecutive days, then a heat advisory will be issued.

An excessive heat warning will be issued when the daytime heat index will be 105 or higher during the day and 75 or higher at night for at least a 48 hour period.  If heat advisory conditions are expected for 4 consecutive days or more (heat indices 100 to 104), then an excessive heat warning will be issued. 

Remember, if heat index values reach 105 degrees or more, sun-stroke, heat cramps or heat exhaustion are likely with prolonged exposure and/or physical activity.

Who is at risk -

Keep in mind that the elderly, small children, people on medication, or with weight or alcohol problems are most susceptible to heat related stresses.  This is especially true during a heat wave in areas where a more moderate climate prevails, such as Wisconsin.  It's a good idea to periodically check in with those most susceptible to the heat and help them obtain relief from the extreme heat and humidity.

Safety Tips -

Here is what you can do to beat the heat:

  • Slow down and reduce outdoor activities, especially during the hottest parts of the day
  • Dress for summer heat: wear lightweight, light colored clothing
  • Do not get too much sun, it makes it even harder for your skin to cool you off.
  • Drink plenty of water and stay away from all alcoholic drinks, which will make the heat's effect on your body even worse.
  • Spend your time indoors. If air conditioning is not available, stay on the lowest floor out of the sunshine. You can also try to go to a public building where air conditioning is available, or sit in a bathtub filled with cool water. In many cases, municipalities will set up cooling shelters.

As with any severe weather, stay tuned to NOAA Weather Radio All-Hazards or your local TV or radio stations for the latest forecast and heat index values.