At what temperature does heat stress become likely during physical activity?

Heat stress becomes likely during physical activity at 105°F due to the body's reduced ability to cool itself effectively at higher temperatures. When the temperature reaches this level, the risk of heat-related illnesses, such as heat exhaustion and heat stroke, significantly increases, particularly when humidity is also high.

At 105°F, the body's mechanisms for dissipating heat, such as sweating and increased blood flow to the skin, may become insufficient, leading to an elevated core temperature that can impair physical performance and pose serious health risks. Understanding these thresholds is crucial for anyone involved in physical activity, especially in warm environments, to prevent dehydration and other heat stress-related complications. This underscores the importance of monitoring environmental conditions when engaging in strenuous activities.