If you have been waiting for OSHA to tell you exactly how hot is too hot, here is the short version: there is still no federal heat standard, there is still no legal maximum workplace temperature, and a proposed rule that would change that has been sitting in the record-review stage since late 2025, with no announced date for a final decision.
That is not the same as saying heat is unregulated. Employers are cited for heat hazards every year, and the number of things an employer is expected to do has not been waiting on the rulemaking. This post covers where the proposed rule actually stands, what it would require if it is finalized, and, more usefully, what is enforceable in your workplace right now.
If you operate in Arizona specifically, it’s worth reading this alongside our post on Arizona’s new statewide heat safety rules, since state requirements can go further than what’s outlined below.
What Applies Right Now
Four things carry legal weight today.
1. The General Duty Clause
Section 5(a)(1) of the Occupational Safety and Health Act requires every employer to furnish a workplace free from recognized hazards likely to cause death or serious physical harm. Heat is a recognized hazard, and there is no serious argument otherwise. NIOSH first published criteria for a recommended heat standard in 1972 and issued a comprehensive revision in 2016. The ACGIH publishes consensus heat exposure limits used across industrial hygiene practice. OSHA maintains its own technical guidance on evaluating heat stress. Half a century of published limits is exactly what “recognized” means.
To cite an employer, OSHA must show a hazard existed, that it was recognized, that it could cause death or serious harm, and that a feasible method of correcting it existed. That last element is usually straightforward in heat cases. Water, rest, a cooler place to recover, and a few days of gradual exposure for new workers are not exotic engineering solutions. When a worker dies of heat stroke, and none of those things were in place, OSHA does not struggle to establish that something feasible could have been done.
2. Existing Part 1910 standards
Several standards apply directly to heat and carry their own citations:
29 CFR 1910.141: potable water must be provided in all places of employment. Common drinking cups and open containers workers dip or pour from are specifically prohibited.
29 CFR 1910.151: medical services and first aid, including a trained first aid provider where no clinic is nearby.
29 CFR 1910.132: the PPE hazard assessment, which must account for heat stress that required protective clothing creates as well as the hazard it prevents.
29 CFR Part 1904: heat-related illnesses are recordable when they result in days away, restricted work, medical treatment beyond first aid, or loss of consciousness. A fatality is reportable within 8 hours; an in-patient hospitalization within 24.
3. The Heat National Emphasis Program
CPL 03-00-024 was reissued on April 10, 2026, and runs for five years, targeting 55 high-risk industries across indoor and outdoor settings. On any day the forecast heat index reaches 80°F, a “heat priority day,” compliance officers are directed to ask about heat hazard prevention, including during inspections opened for entirely unrelated reasons. OSHA also runs programmed inspections when the National Weather Service issues a heat advisory or excessive heat warning.
An NEP is not a standard and creates no new obligation on its own. It determines how likely it is that someone from OSHA walks into your facility and starts asking questions about heat.
4. State plan standards
Seven states already regulate heat beyond the federal baseline. California, Oregon, and Maryland cover both indoor and outdoor work. Washington covers outdoor work. Minnesota sets maximum indoor workplace temperatures by workload. Nevada requires employers above a specified size to have a written heat safety program. Colorado covers agricultural workers. If you operate in any of those states, the federal question is academic. You already have rules.
Where the Proposed Federal Rule Stands
OSHA published the Notice of Proposed Rulemaking for Heat Injury and Illness Prevention in Outdoor and Indoor Work Settings in the Federal Register on August 30, 2024. Since then:
January 14, 2025: the public comment period closed
June 16 through July 2, 2025: OSHA held an informal public hearing across twelve days
October 30, 2025: the post-hearing comment period closed for those who had filed a notice of intention to appear
Since that date, the rulemaking has been in record review. OSHA has not announced a target date for a final rule, and the federal regulatory agenda does not carry a completion date.
This matters for one practical reason: a proposed rule imposes no obligations on anyone. Until a final rule is published and takes effect, nothing in it is enforceable, and no employer can be cited under it.
What the Proposed Rule Would Require
Because the proposal is public, it is worth knowing what it contains, not because it applies, but because it tells you where the agency believes the floor should be.
As proposed, the rule would cover employers in general industry, construction, maritime, and agriculture, both indoors and outdoors. It would exclude short-duration exposures, emergency response operations, indoor work areas kept below 80°F, telework, and indoor sedentary work.
It would set two thresholds:
Initial heat trigger: a heat index of 80°F or equivalent WBGT. At or above that point, employers would provide drinking water and cooling break areas, controls for indoor work areas, acclimatization protocols for new workers, paid rest breaks where needed, and effective two-way communication with employees.
High heat trigger: a heat index of 90°F or equivalent WBGT. Above that, the proposal adds mandatory rest breaks of at least 15 minutes every two hours, observation of workers for signs and symptoms of heat illness, hazard alert reminders, and warning signs in indoor areas that exceed 120°F.
It would also require a written Heat Injury and Illness Prevention Plan covering site-specific hazard identification, heat monitoring procedures, control measures, emergency response, and training, with indoor monitoring records retained at least six months, and everything provided at no cost to employees.
The Number Worth Noticing
The proposed rule’s initial trigger is a heat index of 80°F. The National Emphasis Program’s heat priority day threshold, already in effect and driving inspections, is also a heat index of 80°F.
That is not a coincidence, and it is the most useful thing in this entire post. An employer who builds a heat program around the 80°F threshold today is already aligned with where the agency has said it wants to go. There is no version of the future in which that work is wasted.
Why Waiting Is the Wrong Strategy
The case for acting now does not rest on predicting the rulemaking. It rests on what the enforcement record already shows.
The Centers for Disease Control and Prevention reviewed 25 heat-related enforcement investigations OSHA conducted between 2011 and 2016. Fourteen were fatal. Among those fatalities, 78.6 percent involved workers who were not acclimatized, meaning they were in their first two weeks on the job or returning after more than a week away. Heat stress had exceeded NIOSH-recommended limits in every one of the fourteen deaths.
Six of those fourteen deaths occurred when the heat index was below 91°F.
That last figure deserves attention from anyone who thinks of heat as an extreme-weather problem. Workers do not primarily die on the hottest days of the year. They die on ordinary warm days, early in a job or early in a season, before their bodies have adapted.
Employers also face a cost most never see. A nationwide analysis of workplace injury data published in 2025 attributed roughly 28,000 injuries per year to hot working conditions, with risk climbing at a heat index near 85°F and rising sharply above 90°F, across nearly all industry sectors, including indoor work. The researchers noted the figure is likely an undercount, because injuries caused by heat are normally recorded as falls, struck-by incidents, or equipment accidents rather than as heat cases. A fall from a platform on a hot afternoon is often a heat incident that nobody codes as one.
What to Do Now
None of the following depends on the rulemaking.
Find your heat. Identify where heat is generated indoors and outdoors: furnaces, ovens, dryers, steam lines, trailers and shipping containers, loading docks, routes, and yards. Indoor heat comes from the process, not the weather, and it doesn’t go away in October.
Measure it where the work happens. Weather data describes conditions outside your building. It says nothing about a furnace aisle or a warehouse mezzanine. Measure indoor heat at the work location while the work is happening.
Fix the acclimatization gap first. It is the single highest-return action available, and it is free. New hires, workers back from a week away, seasonal returns, temporary workers, and anyone reassigned to a hotter area all need a graduated schedule.
Make water and rest real. Water that is hot, half a facility away, or empty by mid-shift is not water anyone can use. A break taken beside a furnace is not a rest break in any physiological sense.
Check your emergency response. Heat stroke victims can go into cardiac arrest. Does someone on each shift know to check breathing, start CPR, and cool aggressively on site rather than waiting for the ambulance? Do they know the exact address they would give a dispatcher?
Train your people, and your supervisors. Under the National Emphasis Program, inspectors document whether workers and supervisors actually understand the employer’s heat program. Their answers become part of the record.
What Happens If the Rule Is Finalized
If a final rule is published, it will take effect on a schedule set in the rule itself, and the requirements above become mandatory rather than advisable. Employers that already run a functioning heat program will adjust paperwork. Employers who waited will build a program from scratch during the compliance window, probably in summer.
It is also worth remembering that a final rule would not replace the General Duty Clause. It would simply mean OSHA no longer needs it for heat.
Where Our Training Fits
Our OSHA Heat Stress Training covers what is enforceable today: the General Duty Clause and its four elements, the applicable Part 1910 standards, the National Emphasis Program, and the state plans that go further. It deliberately does not teach the proposed rule, because a course built on a proposal teaches workers requirements that do not exist.
It covers indoor and outdoor heat in one course, all six recognized heat illnesses including rhabdomyolysis, full emergency response with CPR and safe cold water immersion, acclimatization schedules, temporary worker protections, and worker rights under Section 11(c). The three case studies are drawn from published government investigations, not invented scenarios.
If OSHA finalizes the federal rule, we will update the course to reflect it.
Train your crew before the first hot week. Enroll in OSHA Heat Stress Training for indoor and outdoor coverage, real documented case studies, and an instant certificate on completion.
Sources
OSHA, Heat Injury and Illness Prevention Rulemaking (osha.gov/heat-exposure/rulemaking)
OSHA, Proposed Rule Fact Sheet: Heat Injury and Illness Prevention in Outdoor and Indoor Work Settings
OSHA, CPL 03-00-024, National Emphasis Program: Outdoor and Indoor Heat-Related Hazards, reissued April 10, 2026
Tustin AW, et al. Evaluation of Occupational Exposure Limits for Heat Stress in Outdoor Workers, United States, 2011 to 2016. MMWR, 2018
A Nationwide Analysis of Heat and Workplace Injuries in the United States. Environmental Health, 2025
NIOSH, Criteria for a Recommended Standard: Occupational Exposure to Heat and Hot Environments (Publication 2016-106)
