Which athletes are at higher risk of heat illness?

The NFHS heat and hydration statements (October 2025) say risk is higher for athletes who:

• are unfit or not yet used to the heat (poorly acclimatized)
• have obesity or a high body-fat percentage
• are ill or were recently ill, especially with vomiting, diarrhea or fever
• take certain medications that affect hydration or temperature control
• have had exertional heat illness before
• have sickle cell trait
• play football, especially linemen

"Salty sweaters", who leave visible salt stains on clothes and skin, often have a higher risk of exertional muscle cramps.

NFHS says coaches should keep each athlete's conditioning and medical status in mind and adjust their activity to match. Parents: make sure the coach (and the athletic trainer, if there is one) knows about any of these, including a recent illness or a new medication.