According to National Weather Service figures, heat killed 199 Americans last year. That is more than double the second leading cause of weather-related deaths in the United States, flooding, which killed 89 Americans in 2024. The danger posed by weather events like tornadoes, hurricanes and lightning is straightforward, but many people do not accurately perceive the level of risk posed by heat. A day with dangerous heat will look like an average sunny day, and sometimes the symptoms of heat illness are initially ignored.
Heat illness goes through three separate phases. The first phase is dehydration, followed by heat exhaustion and heat stroke. Dehydration is when the body is not getting enough fluids to function correctly. On a hot day, dehydration is caused by excessive sweating. As dehydration begins, the victim will usually feel thirst, followed by more symptoms as dehydration intensifies. Additional dehydration symptoms include the following: dry mouth, lack of urine or dark yellow urine, muscle cramps, low blood pressure, headache, fatigue. As the severity of dehydration builds, other symptoms like dizziness, rapid heart rate and rapid breathing, fainting and lack of sweat become more common.
Without intervention, dehydration symptoms can worsen as the body loses more water and salt to sweat. As dehydration progresses to the next phase, heat exhaustion, many symptoms are similar to dehydration, but just more severe and debilitating. Heat exhaustion symptoms include the following: dizziness or briefly passing out, nausea, being overly tired and weak, heavy sweating or clammy skin and finally higher body temperature.
As body heat continues to rise, heat exhaustion can lead to the more serious condition: heat stroke. When someone has heat stroke, their body temperature has risen to 106 degrees, which can lead to death or permanent disability. If a person is showing any of the signs of heat stroke, it's time to seek emergency medical care. As heat stroke begins, the person will no longer be able to sweat, and may actually feel chills despite their dangerously high body temperature. Other heat stroke symptoms to look for include confusion with slurred speech and possibly a loss of consciousness, hot and dry skin, seizures, rapid heart rate and a body temperature over 104 degrees.
Anyone can develop heat stroke, but some people are more vulnerable than others. Older adults and children are more sensitive to heat stress as well as those who are overweight or have pre-existing health risks like a heart condition or diabetes. The best way to treat heat illness is to avoid it by limiting exposure to extreme heat, drinking more water and taking breaks. Once a person begins to show more serious symptoms of heat exhaustion, other interventions are necessary including moving to shade or a cooler location and using water to directly cool the skin to begin reducing body temperature.