Excessive Heat, Lightning Can Pose Serious Summer Dangers

Sunday marked the start of Missouri Summer Safety Week, which coincides with National Lightning Awareness Week.

The dangers of excessive heat and lightning need to be taken seriously, experts say.

That’s the message meteorologists and health and emergency management officials are hoping to get out during Missouri Summer Weather Safety Week, which coincides with National Lightning Awareness Week. The awareness campaign comes just days after the St. Louis area was under a three-day excessive heat warning.

Dr. John Vandover, assistant medical director of the Emergency Room at St. Anthony’s Medical Center, said he couldn’t provide an exact number of patients treated for heat-related illnesses during last week’s heat wave.

“But we did see a mild increase in the number of minor cases with the heat wave,” he said. “Plus, the heat worsens some chronic medical conditions.”

Vandover said dehydration is the main cause of heat-related illnesses and the best advice if you have to be out is to drink plenty of water, even if you’re not thirsty.

“With heavy exertion, you can lose between one and two liters of fluid each hour without feeling thirsty,” he said. 

Jim Kramper, warning coordination meteorologist with the St. Louis National Weather Service (NWS), said many people underrate the seriousness of excessive heat and lightning compared to other weather events, such as wind, hail, and tornadoes. He added that the number of deaths, illnesses and injuries related to the dangers is underreported.

“The information is hard to gather because you have to check with doctors and hospitals and go over coroner reports,” he said. “I suspect the number of deaths is much bigger than we think.”

There were 17 heat-related deaths in Missouri in 2010, according to the Missouri Department of Health and Senior Services. Between 2000 and 2010, there were 233 heat-related deaths - an average of 23 deaths each year.

Excessive Heat

The St. Louis NWS uses the Heat Index (HI) when determining what temperature it would feel like to an average-sized person wearing light clothing in the shade with winds at 5 mph. To find the HI, meteorologists use a table (see attached pdf file) that takes into consideration the actual air temperature and the percentage of relative humidity. 

The NWS issues the following advisories, warnings and watches when the temperatures rise:

  • Excessive Heat Advisory: This means the HI is expected to reach 105 degrees or the HI will be between 100 and 104 degrees for at least four days.
  • Excessive Heat Warning: When a warning is issued, the HI is expected to reach 110 degrees for two consecutive days or will be around 105 degrees for at least four consecutive days.
  • Excessive Heat Watch: A watch is issued when it is predicted that warning criteria may be met in upcoming days.

For more information on extreme heat and first aid tips, visit the Center for Disease Control and Prevention website.


While many consider lightning fascinating to watch, it is extremely dangerous. The NWS estimates that one strike can generate between 100 million and 1 billion volts of electricity.

Last year in Missouri, lightning was the cause of one death and seven injuries, according to the state NWS. Between 1959 and 2010, there have been 94 deaths attributed to lightning in Missouri or an average of two deaths a year. Meanwhile, the average number of deaths caused by tornadoes during the same period is four.

The National Severe Storms Lab estimates that 51 percent of all lightning incidents occur in open and high elevation areas, such as sports fields and golf courses. Another 29 percent of lightning incidents occur under trees or on water.

The best advice to steer clear of lightning is to stay indoors away from windows, doors and metal pipes. For additional lightning safety tips, visit the NWS website.


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