The summer of 2026 is shaping up to be another record heat-stress season — and federal regulators are watching. Between April 2022 and December 2024, OSHA inspectors completed roughly 7,000 heat-related inspections, issued more than 1,300 hazard alert letters, and removed nearly 1,400 workers from dangerous hot worksites. Yet despite that enforcement push, the United States still has no federal heat standard. Citations land under Section 5(a)(1) of the OSH Act — the catch-all "General Duty Clause" — because there is no specific regulation to cite.
That is about to change. OSHA published a Notice of Proposed Rulemaking for a national Heat Injury and Illness Prevention standard on August 30, 2024, ran a virtual public hearing through July 2, 2025, and closed the post-hearing comment period on October 30, 2025. The proposal sits on the unified regulatory agenda without a final rule date, but enforcement continues aggressively under the National Emphasis Program (NEP), which OSHA renewed in April 2026 for another five years.
Smart employers are not waiting. The compliance blueprint inside the proposed rule already maps to what the General Duty Clause expects today, and five state plans — California, Washington, Oregon, Nevada, and Maryland — have enforceable standards on the books right now. If you employ outdoor crews or run hot indoor operations, here is the playbook you can build today regardless of what happens in Washington.
Why a Heat Standard Is Coming (and Why You Cannot Wait for It)
Heat is the single deadliest occupational weather hazard in the United States. The Bureau of Labor Statistics has reported triple-digit fatal occupational injuries from environmental heat in some recent years, with thousands of nonfatal injuries every season. The number is almost certainly understated because heat-related illness is easy to misclassify as "heart attack" or "fell from height" on a death certificate.
OSHA's proposed rule would cover nearly every workplace under federal jurisdiction — general industry, construction, maritime, and agriculture — wherever indoor or outdoor heat exposure exists. The rule is risk-tiered around two trigger thresholds tied to the heat index (a combined temperature-humidity metric) or, where employers prefer, the more accurate wet-bulb globe temperature.
While the rule is stalled, three forces are squeezing employers right now:
- General Duty Clause citations continue to roll out for any heat-related injury or fatality where the employer ignored a recognized hazard.
- State plan programs in CA, WA, OR, NV, and MD impose binding heat illness prevention requirements that, in some respects, are stricter than the federal proposal.
- Workers' compensation carriers, large general contractors, and federal contracting officers increasingly require written heat illness prevention plans as a condition of work.
You can keep using the federal proposal as a free, well-validated compliance template even if it never becomes a final rule.
The Two Trigger Thresholds That Drive Everything
The proposed rule organizes obligations around two heat-index trigger levels. Everything you owe workers — water, shade, breaks, monitoring — escalates at each tier.
Initial Heat Trigger: 80°F Heat Index
When the heat index reaches 80°F (or 26.7°C wet-bulb globe temperature), the initial heat trigger kicks in. At this level, the employer must:
- Provide cool, potable drinking water within easy access — typically interpreted as one quart of water per worker per hour, replenished throughout the shift.
- Provide a break area with shade or air conditioning that can accommodate all workers on break at one time, located as close to the work area as practical.
- Allow and encourage workers to take paid preventive cool-down rest breaks as needed.
- Begin acclimatization for new employees and any worker returning from a 14-day absence.
- Communicate the heat hazard to workers in a language they understand.
High Heat Trigger: 90°F Heat Index
When the heat index hits 90°F (or about 31.1°C WBGT), high-heat protections become mandatory. The rule adds:
- A mandatory 15-minute paid rest break in a cool break area at least every two hours.
- Active heat-illness symptom monitoring through a buddy system, supervisor observation, or two-way communication for solo workers.
- Hazard alerts to workers before each shift, covering forecast conditions and the location of water and shade.
- A daily check-in confirming workers know how to report symptoms and access emergency response.
The two-tier structure means you do not need to redesign your operation for the hottest possible day. You scale the precautions up and down with the forecast.
The Written Heat Injury and Illness Prevention Plan (HIIPP)
The cornerstone document the proposed rule requires from any employer with 10 or more workers is the Heat Injury and Illness Prevention Plan, or HIIPP. Even smaller employers should write one — every state-plan jurisdiction expects something equivalent, and a written plan is the cleanest defense against a General Duty Clause citation.
A defensible HIIPP includes:
- Scope — the work activities, job classifications, and worksites covered.
- Heat metric selection — heat index from the National Weather Service forecast, on-site thermometer readings, or WBGT measurements.
- Identification of covered worksites and heat sources, including indoor radiant heat from ovens, dryers, kilns, engines, or sun exposure.
- Engineering and administrative controls at each trigger level (water, shade, ventilation, fans, schedule shifts, work-rest ratios).
- Acclimatization protocol for new hires and returning workers.
- Heat illness emergency response procedures, including who calls 911, how to direct EMS to the worksite, and the location of cooling equipment.
- Training program covering signs and symptoms of heat illness, first aid, and worker rights.
- Designation of a "heat safety coordinator" with authority to halt work in dangerous conditions.
- Recordkeeping of heat exposure incidents, training rosters, and plan reviews.
The plan must be reviewed annually and after every heat-related incident that results in loss of consciousness, medical treatment beyond first aid, lost workdays, or death. Treat the HIIPP as a living document, not a binder on a shelf.
Acclimatization: The Most Overlooked Element
Heat acclimatization is the body's gradual physiological adaptation to working in hot conditions — increased blood plasma volume, more efficient sweating, lower core temperature at the same workload. Without it, even fit workers can collapse on their first day of summer.
The proposed rule offers two acclimatization options:
- Option A (high-heat-trigger compliance): Apply the full high-heat protections (15-minute breaks every two hours, active monitoring, hazard alerts) to the unacclimatized worker for the first seven days, regardless of the actual heat index.
- Option B (gradual exposure ramp): Limit the new or returning worker to 20% of the normal duration of work in heat on day one, 40% on day two, 60% on day three, 80% on day four, and 100% on day five and beyond.
The 14-day absence trigger is significant. A roofer who took a two-week vacation, a delivery driver returning from medical leave, or a warehouse worker shifted to a hot zone after weeks indoors all require re-acclimatization. Most heat fatalities involve workers in their first week on a hot job.
Build acclimatization into your hiring workflow. Onboarding paperwork should include a heat-acclimatization schedule signed by the worker and supervisor before the first hot shift.
State Plan Programs: Five Jurisdictions With Active Heat Standards
OSHA operates 22 state plans, but five have specifically promulgated heat illness rules that go well beyond General Duty Clause enforcement. If you do business in any of these states, the state rule controls — and is often more demanding than what OSHA proposed federally.
California — Title 8 §3395 (Outdoor) and §3396 (Indoor)
California is the original. Cal/OSHA's outdoor heat standard at Title 8 CCR Section 3395 has applied since 2005 and was strengthened in 2015. It mandates:
- One quart of drinking water per employee per hour, free, fresh, pure, suitably cool, and as close as practicable to the work area.
- Access to shade when temperatures exceed 80°F, and access on request at any temperature.
- A written Heat Illness Prevention Plan in English and the language understood by the majority of workers.
- A "high-heat" trigger at 95°F with additional requirements: effective observation and monitoring, pre-shift meetings, mandatory minimum 10-minute cool-down rest periods every two hours during the high-heat period (one hour in agriculture).
- Acclimatization observation for new workers during the first 14 days, with close observation during heat waves.
In July 2024, Cal/OSHA's indoor heat standard at Section 3396 took effect. It applies whenever the indoor temperature reaches 82°F (or 87°F where workers wear clothing that restricts heat removal or work in radiant-heat areas) and adds engineering controls, administrative controls, and personal heat-protective equipment as the temperature climbs.
Washington — WAC 296-62-095
Washington's outdoor heat exposure rule, updated in 2023, applies year-round any time the temperature reaches 80°F outdoors and adds high-heat triggers at 90°F (15-minute paid rest every two hours) and 100°F (15-minute paid rest every hour). Employers must provide one quart of drinking water per worker per hour and maintain a written Outdoor Heat Exposure Safety Program.
Oregon — OAR 437-002-0156
Oregon's permanent rule, adopted in 2022, applies any time the heat index reaches 80°F. It mandates shade, access to potable water of 1.5 quarts per hour per employee, mandatory rest breaks (10 minutes every two hours at 80°F and 15 minutes every hour at 90°F), an emergency medical plan, and acclimatization plans for new workers. Oregon's high-heat threshold is one of the strictest in the country.
Nevada — NAC Chapter 618
Nevada adopted a heat illness regulation effective in 2024. Employers must perform a written job hazard analysis for any work that may involve heat illness exposure and implement controls. Nevada's standard is process-based rather than threshold-based, but it operates much like a HIIPP requirement.
Maryland — COMAR 09.12.32
Maryland's permanent heat stress rule (under MOSH) took effect in 2024. It applies at a heat index of 80°F and adds high-heat protections at 90°F. Required elements include a written heat-related illness prevention plan, acclimatization, hydration, rest breaks, shade or cooling, and training.
If you operate in multiple states, build your HIIPP to the strictest applicable standard and apply it uniformly. The administrative cost of running parallel programs almost always exceeds the cost of the slightly more conservative single program.
Industries Most at Risk
The federal proposal applies across virtually every industry, but enforcement and incident data point at a handful of sectors as priority targets.
Construction and Roofing
Roofers face the deadliest heat exposure of any trade. Asphalt shingle surface temperatures can exceed 160°F on a 90°F day, and the work is high-exertion with limited shade. General contractors should require subcontractors to certify HIIPP compliance as a contract term, and self-performing GCs need their own HIIPP keyed to each active site's microclimate.
Landscaping and Tree Care
Crews working in full sun, often using engine-driven equipment that adds radiant heat, face the highest per-hour exposure of any outdoor trade. Pair the HIIPP with route planning that schedules the hottest properties for the earliest hours.
Agriculture
Farm workers, especially in the H-2A guestworker program, are the historically highest-risk population. State plans like California's and Oregon's were written largely with agricultural workers in mind. The federal proposal would extend equivalent protection nationwide.
Delivery Drivers and Postal Workers
Last-mile delivery drivers in non-air-conditioned vans (the U.S. Postal Service is the most cited example, but Amazon DSPs and parcel contractors face equivalent risk) absorb heat from both the cab and the package compartment. Vehicle telematics integrated with NWS heat index forecasts can drive route adjustments and break scheduling.
Warehouse and Distribution Center Workers
Non-air-conditioned warehouses can run 10–15°F hotter than the outside ambient temperature on a still summer day. Mezzanines and high-pick zones are even hotter. Engineering controls (ventilation, evaporative cooling, fans), administrative controls (rotating workers in and out of hot zones), and personal cooling (vests, neck wraps) all play a role.
Restaurant Kitchens and Bakeries
Indoor kitchens routinely hit 90°F at the line on a moderate summer day, and 100°F+ in front of open ovens, fryers, and char-broilers. Restaurant operators often misread the proposed rule as outdoor-only — it explicitly covers indoor radiant-heat operations including bakeries, kitchens, laundries, foundries, and electrical utility vaults.
Training and Hazard Communication
Both the federal proposal and every state plan require training before any worker performs work in heat-trigger conditions. A defensible heat training program covers:
- Signs and symptoms of heat illness — heat rash, heat cramps, heat exhaustion, heat stroke — and the difference between them.
- First aid response — cooling, hydration, when to call 911.
- The buddy system and the duty to monitor coworkers.
- The right to a cool-down rest break without retaliation.
- The location of water, shade, and emergency contacts.
- Acclimatization protocols and personal risk factors (medications, prior illness, pregnancy, age).
Supervisors need additional training on heat illness diagnosis, when to stop work, and emergency response coordination. Document every training session with a roster, date, and trainer signature.
The proposed rule and state plans share a critical compliance element: training must be in a language the worker understands. For multilingual crews, that means Spanish, Mandarin, Vietnamese, Tagalog, or other primary languages — not English-only paperwork that everyone signs.
Recordkeeping: Form 300, 301, and the HIIPP File
OSHA's existing recordkeeping rules (29 CFR 1904) already require employers with more than 10 workers to record work-related heat injuries on Form 300, supplement with the 301 incident report, and post the 300A annual summary in February. A heat illness that results in loss of consciousness, medical treatment beyond first aid, days away from work, restricted duty, or transfer to another job is recordable.
The proposed rule layers on heat-specific recordkeeping:
- The HIIPP itself, in writing, accessible to workers.
- Records of acclimatization for each new or returning worker.
- Records of any heat exposure that triggered first aid or further medical attention.
- Records of HIIPP annual reviews and post-incident reviews.
Bookkeeping note: training time, water and shade structure purchases, cooling vests, medical surveillance, and the cost of OSHA-required signage are all deductible business expenses. Track them separately during the year so you can substantiate them at tax time and demonstrate your safety investment if you face an inspection or workers' comp audit.
Build Your HIIPP Before Inspectors Build It for You
The proposed federal rule has not been finalized, and may not be in the current administration. But the General Duty Clause is fully enforceable today, state plans are tightening, and workers' comp carriers are conditioning premiums on heat illness programs. The lowest-cost, lowest-regret path is to build a compliant Heat Injury and Illness Prevention Plan now using the federal proposal as your template, with state-specific overlays where needed.
A practical 30-day rollout:
- Week 1 — Identify covered worksites and job classifications. Pick a heat metric. Assign a heat safety coordinator with stop-work authority.
- Week 2 — Draft the HIIPP. Procure water containers, shade structures or fans, thermometers, and signage. Confirm emergency response procedures with local EMS dispatch.
- Week 3 — Train all workers and supervisors. Translate training materials into the languages your crews actually speak. Roster every session.
- Week 4 — Run a tabletop drill. Walk the worksite at noon, take heat-index readings, simulate a heat-illness incident, and time your emergency response. Revise the HIIPP based on what you learn.
The first 90°F day of the year is not the day to start. Build now.
Keep Your Compliance Records Organized Through Heat Season
Compliance documents, training rosters, equipment purchases, and incident reports pile up fast once a heat program is running — and so do the related expenses. Beancount.io gives you plain-text accounting that's transparent, version-controlled, and friendly to the kind of itemized expense tracking that survives an audit or a workers' compensation review. Get started for free and keep your safety spending defensible alongside the rest of your books.
Sources and Further Reading
- OSHA, Heat Exposure rulemaking page
- OSHA, Proposed Rule Fact Sheet on Heat Injury and Illness Prevention
- Cal/OSHA, Title 8 CCR Section 3395 — Heat Illness Prevention in Outdoor Places of Employment
- Cal/OSHA, Title 8 CCR Section 3396 — Heat Illness Prevention in Indoor Places of Employment
- Washington L&I, WAC 296-62-095 — Outdoor Heat Exposure
- Oregon OSHA, OAR 437-002-0156 — Heat Illness Prevention
- Maryland MOSH, COMAR 09.12.32 — Heat Stress Standards