There is no federal OSHA heat standard. There is a General Duty Clause, a national enforcement program with an eleven-point checklist, seven states with their own rules, and a proposed federal rule that has not become law. That combination is why heat gets cited every summer even though no regulation says "80 degrees."
The short answer: no federal heat standard yet
OSHA published a Notice of Proposed Rulemaking, Heat Injury and Illness Prevention in Outdoor and Indoor Work Settings, in the Federal Register on August 30, 2024 (89 FR 70698). The public comment period closed on January 14, 2025. An informal public hearing ran from June 16 to July 2, 2025. The post-hearing comment period for participants who filed a Notice of Intention to Appear closed on October 30, 2025. As of the update date on this page, no final rule has issued.
That matters in one direction only. A missing standard does not mean heat is unregulated; it means there is no checklist you can point to and say "we did the eight things the rule lists." What replaces it is a performance obligation, judged after the fact.
What actually applies today
The hook is Section 5(a)(1) of the OSH Act, the General Duty Clause: every employer must furnish a workplace "free from recognized hazards that are causing or are likely to cause death or serious physical harm." OSHA's own heat standards page says the courts read that to mean a hazard the employer or the industry recognizes, that causes or is likely to cause death or serious physical harm, and for which a feasible method of abatement exists. Heat qualifies on all three, which is exactly why heat cases are winnable for the agency without a heat rule.
Several ordinary standards also land on hot work, and they are easier to cite than the General Duty Clause because they say something specific:
| Standard | What it requires |
|---|---|
| 29 CFR 1926.51, 1910.141 | Potable water at the workplace (also 1915.88, 1917.127, 1918.95, 1928.110) |
| 29 CFR 1926.50, 1910.151 | Medical services and first aid: trained persons on site where no medical facility is close by |
| 29 CFR 1910.132(d), 1926.28, 1926.95 | PPE hazard assessment - and OSHA has a 1998 letter of interpretation naming heat stress as a factor in it |
| 29 CFR 1926.21 | Safety training and education in construction |
| 29 CFR 1904 | Recording heat illnesses; 1904.39 reporting of fatalities and hospitalizations |
How OSHA enforces heat: the National Emphasis Program
OSHA Directive CPL 03-00-024, the National Emphasis Program for outdoor and indoor heat-related hazards, took effect on April 10, 2026, superseding the 2022 program. It covers general industry, construction, maritime and agriculture. Two mechanics decide whether it touches your site:
- Heat priority day. A day when the heat index is expected to be 80 degrees Fahrenheit or more. On those days, a compliance officer already on your site for any other reason is directed to ask whether a heat-related hazard prevention program exists.
- NWS alerts. Programmed inspections "shall occur on any day that the NWS has announced a heat warning or advisory for the local area," drawn from target industry lists in the directive's Appendix A.
The scale is not theoretical. The directive reports that heat-related inspections accounted for 6 percent of all federal inspections over the previous five years, split 57 percent programmed and 43 percent unprogrammed. The 2025 notice extending the earlier program counted approximately 7,000 heat-related inspections between April 8, 2022 and December 29, 2024, 60 General Duty Clause citations for heat, and 1,392 Hazard Alert Letters. The gap between 7,000 inspections and 60 citations is the General Duty Clause being hard to prove - not heat being tolerated.
The eleven questions you are actually being graded on
Appendix I of the directive, "Evaluation of a Heat Program," is the list a compliance officer works through. It is the closest thing to a federal heat standard that exists today, and it is public:
| # | What the compliance officer determines |
|---|---|
| 1 | Is there a heat program, written or verbal, effectively communicated to employees? |
| 2 | How did the employer monitor ambient temperature and levels of work exertion? |
| 3 | Were there sufficient amounts of cool water easily accessible? |
| 4 | Did the employer allow additional breaks for hydration? |
| 5 | Were there scheduled rest breaks? |
| 6 | Was there access to a shaded area? |
| 7 | Did the employer provide time for acclimatization of new and returning workers? |
| 8 | Were administrative controls used - earlier start times, workload adjustments, job rotation? |
| 9 | Training on signs, reporting, first aid, contacting emergency personnel, prevention, hydration? |
| 10 | Do employees and supervisors understand the heat program? |
| 11 | Is the program implemented and managed by a designated heat safety representative? |
Note what the inspection also pulls: the directive tells officers to review OSHA 300 logs and 301 reports for heat entries, to look for emergency room visits or ambulance transports even where nobody was hospitalized, and to interview workers about headache, dizziness, fainting and dehydration - including new employees and anyone recently returned to work. The heat illness prevention plan generator is built section by section against this same list.
When is it too hot? The numbers OSHA publishes
OSHA recommends measuring wet bulb globe temperature on site, because it accounts for temperature, humidity, radiant heat and air movement, while the heat index is measured in the shade and accounts for two of the four. You then add a clothing adjustment factor to get the effective WBGT and compare it with limits that depend on workload and on whether the worker is acclimatized. Anyone doing the job less than one to two weeks is treated as unacclimatized.
| Workload | Unacclimatized (action limit) | Acclimatized (threshold limit value) |
|---|---|---|
| Light - minimal arm and leg work, occasional walking | 82.4 °F (28 °C) | 86 °F (30 °C) |
| Moderate - normal walking, hammering, general carpentry | 77 °F (25 °C) | 82.4 °F (28 °C) |
| Heavy - carrying loads, shoveling, sawing, roofing | 73.4 °F (23 °C) | 78.8 °F (26 °C) |
| Very heavy - intense digging, sledgehammer, masonry | 69.8 °F (21 °C) | 77 °F (25 °C) |
Clothing adjustment factors from the same page: work clothing and cloth coveralls add nothing; SMS coveralls add 0.9 °F; polyolefin coveralls 1.8 °F; double-layer cloth 5.4 °F; limited-use vapor-barrier coveralls 19.8 °F. A crew in vapor-barrier suits at 60 °F is at an effective WBGT near 80.
If you are screening a forecast rather than metering a site, the heat index and work/rest calculator turns temperature and humidity into a heat index and the matching OSHA category in a few seconds.
What OSHA expects to find on the ground
OSHA's Planning and Supervision page frames the program as eight questions to settle before the hot day: who provides oversight daily; how new workers gradually develop heat tolerance; how first aid stays adequate and the protocol for summoning medical help beyond first aid stays effective; what engineering controls and work practices will be used; how heat stress will be measured; how to respond to an NWS advisory or warning; how total heat stress is judged hazardous; and what training workers and supervisors get.
Four of those get almost every citation, and each has a concrete published expectation:
- Water. Cool potable water near the work, in a familiar and easy-to-reach location, in sufficient quantity for the duration of the work. For jobs longer than two hours, add beverages that contain electrolytes: sweat carries salt out, and water alone does not put it back.
- Rest and shade. Breaks whose length and frequency increase as heat stress rises, taken in shade, an air-conditioned vehicle, a building, a tent, or an area with fans and misting. Breaks last longer when there is nowhere cool to sit, because recovery is slower.
- Acclimatization. The Rule of 20 Percent: a worker new to the heat works 20 percent of the normal duration on day one and adds 20 percent each day, reaching a normal schedule by the end of the first week. Reduce duration, not intensity - light duty does not prepare anyone for heavy work in heat.
- Supervision. One person on site, named and trained, who monitors conditions and runs the plan through the workday, and who knows how to identify and control heat hazards, recognize early symptoms, administer first aid, and activate EMS quickly.
And when someone shows symptoms, OSHA's instruction is not to diagnose. Move the worker somewhere cooler, cool them actively - cold water or ice bath immersion is described as the best method for rapid cooling, with ice or cold wet towels on head, neck, trunk, armpits and groin - never leave them alone, and when there is confusion, slurred speech or unconsciousness, call 911 immediately and keep cooling until help arrives.
Where state rules override the federal blank
State Plans must be at least as effective as federal OSHA and may require more. On heat, several do, and their obligations are real regulations rather than guidance. OSHA's heat standards page names California, Colorado, Minnesota, Oregon and Washington; Maryland's standard came later, and Nevada's later still.
| State | Note |
|---|---|
| California | Heat illness prevention standard; OSHA notes a temperature of 80 °F triggers the requirements |
| Colorado | Agricultural Labor Conditions Rules |
| Maryland | COMAR 09.12.32, effective September 30, 2024; applies where the heat index is 80 °F or higher |
| Minnesota | Applies to indoor places of employment |
| Nevada | Heat illness regulation R131-24, enforced from April 29, 2025 |
| Oregon | Applies indoors and outdoors, including construction and forest activities |
| Washington | Outdoor heat exposure rule |
If you work across state lines, the practical answer is to build one program to the strictest rule you touch rather than seven programs, and to note in the plan which state rule drove which number.
What the proposed federal rule would add
This section describes a proposal in an open rulemaking. None of it is enforceable, and a final rule can differ from what was proposed.
As published in August 2024, the proposed standard would be a programmatic rule applying to outdoor and indoor work across general industry, construction, maritime and agriculture, with some exceptions. Employers would build a heat injury and illness prevention plan and act at two trigger levels: an initial heat trigger at a heat index of 80 °F and a high heat trigger at 90 °F. OSHA explained the choice by pointing at states that already work that way: 80 and 90 match Oregon's existing standard, while California and Colorado use ambient temperature triggers of 80 and 95, and Washington uses 80 and 90 ambient for workers in ordinary clothing.
The useful takeaway for a contractor is not the number. It is that a written plan, acclimatization, water, rest, shade, monitoring and training show up in every state rule and in the federal proposal alike. A program built on those does not have to be rebuilt when a final rule lands.
Four mistakes that turn a hot day into a case
- Waiting for the forecast to say 95. Heat stroke deaths have happened at a maximum heat index of 86 °F, and heavy work pushes the effective limit down to the low 70s for a crew that is not acclimatized.
- Treating the new guy like the crew. Half of heat deaths land on day one. A worker who "looks fit" is not acclimatized, and neither is the veteran back from a week of vacation.
- Water on site, but 300 feet away. OSHA's expectation is water near the work, familiar, easy to reach, in sufficient quantity. A cooler in the trailer is not access; it is a walk that nobody takes twice.
- A plan nobody has heard. The first Appendix I question is whether the program is effectively communicated to employees, and question ten asks whether employees and supervisors understand it. A binder in the office answers neither.
Bottom line
- No federal heat standard exists; the proposed rule has been through hearings and post-hearing comments and is not final.
- Heat is cited under the General Duty Clause, and the water, first aid, PPE, training and recordkeeping standards apply on their own terms.
- The heat NEP effective April 10, 2026 sets a heat priority day at a heat index of 80 °F and sends programmed inspections out on NWS advisory days.
- Appendix I of that directive is the eleven-point checklist your program is measured against - and it is public, so build to it.
- If your state has its own heat rule, that rule is the one you comply with; federal guidance is the floor.
Put the eleven points on paper before the next hot week with the free heat illness prevention plan template, then brief it with the heat stress toolbox talk so the crew has heard it in their own words.