Heat Illness Prevention: Employer Obligations and Best Practices

An Evolving Regulatory Landscape

Heat-related illness kills dozens of workers annually and sickens thousands more. OSHA published a notice of proposed rulemaking on heat injury and illness prevention on August 30, 2024, with initial and high-heat trigger thresholds at heat indexes of 80 and 90 degrees Fahrenheit. As of 2026 the rule has not been finalized; the post-hearing comment period closed October 30, 2025 and the rulemaking has effectively stalled. OSHA renewed and updated its Heat-Related Hazards National Emphasis Program in April 2026, so enforcement under the General Duty Clause continues. Several states, including California, Washington, Oregon, Colorado, Nevada, Maryland, and Minnesota, already have specific heat illness prevention standards.

Employers in construction, agriculture, landscaping, warehousing, manufacturing, and any industry with significant heat exposure must take this issue seriously. Even office-based employers can face exposure when HVAC systems fail or employees work in non-climate-controlled spaces.

Understanding Heat-Related Illness

Heat illness occurs on a spectrum from mild to life-threatening:

• Heat rash: Skin irritation from sweating in hot, humid conditions
• Heat cramps: Painful muscle spasms caused by heavy sweating and electrolyte loss
• Heat exhaustion: Heavy sweating, weakness, nausea, dizziness, and cool/clammy skin
• Heat stroke: A medical emergency with body temperature above 103 degrees, confusion, loss of consciousness, and potentially death

Employers must train workers and supervisors to recognize these conditions and respond appropriately. Heat stroke requires immediate emergency medical attention.

Key Elements of a Prevention Program

Written Heat Illness Prevention Plan

Develop a written plan that covers your specific workplace conditions. Include the triggers for activating the plan (temperature thresholds), specific procedures, and assigned responsibilities. California requires a written plan specifically for outdoor workers; even where not legally required, a written plan demonstrates due diligence.

Water

Provide fresh, cool drinking water at no cost to employees, positioned so that workers can access it without unreasonable delay. The general guidance is that employers may consider providing one quart of water per employee per hour in hot conditions. Employers should consult state-specific regulations for precise requirements and should not rely on employees bringing their own water.

Rest and Shade

Provide access to shade or a cool rest area where workers can recover. California's standard requires shade when temperatures exceed 80 degrees Fahrenheit and allows employees to take preventive cool-down rest periods of at least five minutes. Do not discourage employees from taking rest breaks when they feel overheated.

Acclimatization

New employees and those returning from extended absence are at significantly higher risk. Implement an acclimatization plan that gradually increases new workers' exposure over a period of at least one to two weeks. During heat waves (sudden temperature increases), apply acclimatization procedures to all workers, not just new hires.

Training

Train all employees and supervisors on:

• Risk factors for heat illness, including personal factors like medications and fitness level
• Signs and symptoms of heat-related conditions
• How and when to call for medical help
• First aid procedures
• The importance of hydration and reporting symptoms early
• Emergency response procedures

Emergency Response

Establish clear procedures for responding to a heat illness event. Ensure that emergency medical services can access the worksite, that someone is designated to call 911, and that first aid measures (moving the worker to shade, cooling with water, removing excess clothing) begin immediately.

Monitoring

When conditions are severe, implement a buddy system so that workers can monitor each other. Consider work-rest schedules that reduce exposure during the hottest parts of the day. Use wet bulb globe temperature (WBGT) measurements rather than simple air temperature for a more accurate assessment of heat stress risk.

Indoor Heat Hazards

Heat illness is not limited to outdoor work. Warehouses, kitchens, laundries, foundries, and manufacturing facilities can generate dangerous heat levels. If your indoor workplace lacks adequate climate control, the same prevention principles apply. Assess the heat conditions, provide water and rest, and train employees.

Enforcement Activity

OSHA's renewed Heat National Emphasis Program (effective April 2026 for five years) means inspectors are actively looking for heat-related hazards. Even without a finalized federal standard, OSHA can and does cite employers under the General Duty Clause (Section 5(a)(1)) for failing to protect workers from recognized heat hazards. State-plan states with specific heat standards conduct even more targeted enforcement.

Do not wait for a federal standard to act. The tools for preventing heat illness are straightforward, and the cost of a comprehensive prevention program is far less than the cost of a worker's serious illness or death.