Heat Illness Prevention & Sun Safety

Last Updated: April 10, 2024
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Soldier in desert


Those who work outside are at greater risk of heat related illness and injury – heat illness is particularly a concern since average temperatures have been notably high the last two decades (see article).​​External Link 

Military personnel are at high risk for heat illness, especially during rigorous physical outdoor training. Because of the added heat stress from the body during vigorous activity, the military refers to heat-related medical conditions as ‘exertional heat illness’ or EHI

EHI refers to conditions that can occur when your body overheats, ranging from dehydration and mild heat cramps, to a more serious medical condition called heat exhaustion, to the life-threatening medical emergencies heat stroke and hyponatremia (a condition when excessive water consumption causes an imbalance to the body’s chemistry). Failure to prevent milder conditions from progressing can result in more serious heat casualties, including death. 

Though Service members may be relatively young and healthy, hundreds of military EHI or ‘heat casualties’, including 1 to 3 deaths, occur each year. 

​S​ee the DCPH-A Heat Illness Prevention Guide for Service Members as a quick reference to reduce risk of EHI. This guide is based on the 2022 major update to TB Med 507​External Link, the Army’s heat casualty prevention doctrine manual. 

What are the risk factors? 

In addition to environmental factors, strenuous activity duration and frequency and individual factors impact a person's risk of developing a heat illness: 

  • ​High heat is a primary EHI hazard, so most EHIs occur between May and September, especially when the outside temperature is over 75° Fahrenheit (F). In addition to the temperature, sunlight, humidity, and wind speed all affect heat illness risk. 
  • The amount of time exposed and number consecutive days of strenuous activities in high heat increases the risk of an EHI. 
  • Individuals may also have factors that increase their susceptibility to heat illness. For example, having a heat illness one time (heat cramps, heat exhaustion, heat stroke) increases a person's susceptibility to future heat-related illness – even one that is more severe. Certain health conditions, fitness level, medications, nutrition and hydration are examples of other factors that can influence individual risk levels of EHI.​

​News Articles: 

Click banner to learn about the types of heat illnesses


Heat Illness Impacts Readiness

Heat illness, and dehydration from vigorous activity in heat, is a threat to individual health and to military operational success. Some supporting facts: 

  • Since 2014, more than 1,500 Soldiers each year have developed a heat illness that required medical attention and/or lost duty time 
  • Heat illnesses were responsible for more than 20,500 lost/limited duty days in 2017 
  • Losing as much as 4% of body weight from dehydration can degrade physical performance 
  • Every 1% loss of body weight increases core temperature (0.10-0.23⁰C or 0.18-0.40⁰F), thereby increasing risk of a more serious heat illness

Army Heat Illness Factsheet

 Click banner to view Exertional Heat Illness video on YouTubeExternal Link 

Link to video on milTube, with captions (CAC required)External Link


Click banner to view DCPH-A Heat Related Injury Reports

The most severe types of heat illness (heat stroke and heat exhaustion) are military Reportable Medical Events (RME). Cases of these two types of heat illness documented in this medical system are reported by the military: