America's Top Weather Killer Is Not Tornadoes, Flooding, Lightning Or Hurricanes – It's Heat

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Extreme heat is responsible for more weather-related deaths in the United States in an average year than any other hazard.

Excessive heat claimed an average of 158 lives per year in the U.S. from 1992 through 2021, according to NOAA. That's higher than the average annual death tolls from flooding (88), tornadoes (71), hurricanes or tropical storms (45) and lightning (37) in that 30-year period.

You may be surprised by this.

In 2005, Hurricane Katrina was responsible for 1,500 deaths in the U.S., according to the National Hurricane Center.

The April 2011 Super Outbreak of tornadoes killed 324 in the Southeast. One month later, an EF5 tornado in Joplin, Missouri, was blamed for 158 deaths.

Other than those outlier deadly weather disasters, heat deaths in the country typically outnumber other hazards. That's been the case, particularly since the late 1990s, as the graph below shows.

Flooding remains the No. 2 killer. Flash flooding can occur almost anywhere in the U.S., and given the continued problem of flood deaths in vehicles, this is not surprising.

Tornado warnings and Doppler radar have reduced tornado fatalities markedly since the early 20th century. Since 2010, lightning deaths have plummeted, to 20 or fewer each of the past five years.

A Different Kind of 'Storm'

Heat tends to be most impactful and deadly in the form of a heat wave, any period of anomalous and uncomfortably hot and humid weather that lasts several days to weeks at a time.

A heat wave doesn't have to shatter temperature records to be dangerous. How long it lasts is at least as important as how hot it gets.

One reason for this is how little it may cool down at night, particularly in larger cities.

Heat absorbed by a city's concrete and asphalt during the day is released more slowly at night, which can make urban areas up to 22 degrees hotter than surrounding rural areas, a phenomenon known as the urban heat island.

In a typical summer heat wave, overnight low temperatures may dip only into the upper 70s or low 80s in a larger city in the Northeast, Midwest or South.

Those living in the heart of a city may not have air conditioning or are fearful to open windows at night for safety reasons.

A fan may be of little help, as that may only blast and recirculate hot, humid air.

There may be no break in the heat at night, perhaps for days.

As heat stress builds, heat exhaustion could eventually lead to heat stroke, as the body's temperature climbs above 103 degrees, requiring immediate medical attention.

Everyone is susceptible to heat exhaustion or heat stroke, but the elderly, infants and children are particularly vulnerable.

In July 1995, a heat wave pushed high temperatures into the mid-90s to mid-100s in Chicago for five days. It was accompanied by oppressive humidity. Overnight lows at Chicago's Midway Airport failed to drop below 76 degrees.

At least 465 deaths in Chicago were attributed to the heat wave, according to NOAA's National Disaster Survey Report. In all, NOAA concluded more than 1,000 died from this Midwest heat wave. Most of the victims were elderly and confined to their homes and apartments without air conditioning. Hospitals weren't prepared to deal with the large volume of patients.

The report found that even though temperature forecasts for the area were accurate, local government and services failed to view the situation as a threat to public health. As a result, there was no communication to the public regarding the dire consequences for sensitive groups.

Since 1995, local governments have taken measures to prepare for heat events.

Better lines of communication exist between local governments, public safety officials and the local National Weather Service. There is also much better communication about preparing for the heat and what measures can be taken when it arrives.

Cooling stations and shelters are now set up in cities when excessive heat becomes an issue.

The National Weather Service has also unveiled an experimental HeatRisk product for the western U.S. that breaks down potential heat impacts into categories of severity. It will likely be rolled out nationally in the coming years.

Safety Tips

The first line of defense against extreme heat is to be aware of the forecast.

The National Weather Service issues excessive heat watches and warnings when the combination of heat and humidity is expected to pose a danger. When a warning is issued, it's time to take action.

Here are some important safety tips from the Centers for Disease Control and Prevention:

• Stay in air-conditioned buildings as much as possible.
• Don't rely on a fan as your main cooling source when it's very hot outside.
• Drink more water than usual and don't wait until you are thirsty to drink.
• Don't use the stove or oven to cook – it will make you and your house hotter.
• Wear loose, lightweight, light-colored clothing.
• Take cool showers or baths to cool down.
• Don't engage in very strenuous activities and get plenty of rest.
• Check on a friend, neighbor or family member, especially the elderly – and have someone check on you.

Hotter Future

According to a study of 246 U.S. locations by Climate Central, 96% of those have seen their summer temperatures increase since 1970.

The study found the strongest heating has been in the Southwest.

Another recent study found that more than one-third of heat-related deaths worldwide are directly connected to human-induced climate change. So the danger from heat waves appears to be increasing.

Treat an approaching heat wave with the same urgency as you would a tornado outbreak or hurricane. It could save someone's life.

The Weather Company’s primary journalistic mission is to report on breaking weather news, the environment and the importance of science to our lives. This story does not necessarily represent the position of our parent company, IBM.