Heat stress on construction sites can cause dehydration, heat exhaustion, and life-threatening heat stroke. Employers must implement controls to reduce heat stress exposure including scheduling heavy work during cooler parts of the day, providing shade and rest areas, ensuring adequate water intake, and monitoring workers for signs of heat illness. Water must be readily available and workers must be encouraged to drink regularly to maintain hydration. Cool rest areas must be provided where workers can reduce their body temperature. Employees must be trained to recognize symptoms of heat illness including heavy sweating, weakness, dizziness, nausea, and confusion. If heat illness is suspected, the worker must be moved to a cool area and given water to drink. Severe cases require emergency medical response. Acclimatization to hot environments is important; workers new to hot work must gradually increase exposure over 7-14 days. Workers returning from illness or absence must undergo acclimatization again. Lightweight, light-colored, loose-fitting clothing allows sweat evaporation. Supervisors must monitor workers and reduce activity levels during high heat conditions. Physical fitness and age affect heat tolerance; older workers and those with existing medical conditions require additional monitoring. Outdoor work during extreme heat warnings must be postponed or work modified to minimize exposure. OSHA's heat illness prevention guidelines recommend work-rest cycles with frequent breaks in shade or air conditioning. Indoor work areas must have adequate ventilation and cooling to prevent heat stress.