(NewsNation) — Heat waves, like the ones seen by over 100 million people across the country this week, are the leading cause of weather-related deaths in the U.S. High temperatures, on average, cause more fatalities than other kinds of hazardous weather events, like floods or tornadoes.

More than 600 people in the United States are killed by extreme heat every year, according to the Centers for Disease Control and Prevention. By comparison, the National Weather Service reports that about 80 tornado deaths a year are reported. In 2021, 145 people were killed in floods.

Heat-related conditions, per the CDC, include heat exhaustion, heat stroke, and hyperthermia, where exposure to extreme heat causes the body to become unable to property cool.

In serious cases, heat-related illnesses can be life-threatening, shutting down organs or exacerbating preexisting conditions. Symptoms of heat exhaustion can include:

  • Muscle cramping
  • Fatigue
  • Headache
  • Nausea or vomiting
  • Dizziness or Fainting

In more severe cases where heat exhaustion leads to heat stroke, symptoms can also include raised body temperature (of 103 degrees F or higher); a rapid, strong pulse; confusion; and unconsciousness, according to the CDC.

People at greatest risk of a heat-related illness include infants and children up to 4 years old, as well as people older than 65, those living in poverty, people who are socially isolated, and people with existing medical conditions, such as diabetes or heart disease.

To beat the heat, experts recommend drinking plenty of water and avoiding the sun. The CDC also advises wearing sunscreen when outdoors, choosing lightweight, light-colored, loose-fitting clothing, and staying in air-conditioned spaces. Those who live in homes without air conditioning might even be eligible for assistance.