Quick Answer
OSHA does not set a specific legal maximum indoor temperature for most workplaces. Instead, employers are required under the General Duty Clause to protect employees from recognized hazards — including excessive heat. OSHA recommends indoor workplaces stay between roughly 68°F and 76°F for comfort, and treats heat index readings above about 80°F as the point where heat illness prevention measures should begin. A proposed federal heat rule, expected to move forward in 2026, would formalize specific triggers, water, rest, shade and acclimatization requirements for both indoor and outdoor work.
Why it matters
Small business owners frequently ask a version of the same question every summer: is there a legal temperature at which I have to send my staff home? The honest answer is more useful than a single number. OSHA holds employers accountable for keeping workplaces free of recognized hazards, and excessive heat — especially in warehouses, kitchens, factories, and delivery vehicles — is one of the most consistently cited under that general duty.
Understanding what the rules actually say helps owners make calm, defensible decisions instead of guessing. It also puts you ahead of the federal rulemaking now moving through the process. Businesses that put simple heat controls in place today will not need to scramble when the standard is finalized — and their staff will be safer in the meantime.
Detailed guide
Introduction
Heat is the leading weather-related cause of workplace injury in the United States, and indoor heat is consistently the most underestimated form of it. A warehouse in the afternoon, a commercial kitchen during a lunch rush, or a manufacturing floor next to a heat-generating machine can easily exceed the temperatures that cause serious harm — often without any of the obvious cues that prompt action outdoors.
This guide answers the questions small business owners and managers actually ask about OSHA's indoor temperature rules: what the law requires today, what is changing, and what you can do this week to reduce risk. It is written for non-lawyers and non-safety-professionals, in plain English, without legal advice or fear.
Does OSHA set a maximum indoor temperature?
No. OSHA does not currently set a specific legal maximum indoor workplace temperature that applies across the country. There is no federal number you can point to and say 'above this, we close.' That surprises many owners, because state and industry rules for schools, food service and healthcare often do include specific numbers.
What OSHA does provide is a recommended comfort range of roughly 68°F to 76°F for typical office environments, along with humidity guidance in the 20 to 60 percent range. These are recommendations, not enforceable limits. For workplaces that routinely operate outside those ranges — warehouses, kitchens, manufacturing, retail stockrooms, laundries — the relevant standard is not a number, it is a duty.
What OSHA actually requires
Under the General Duty Clause (Section 5(a)(1) of the OSH Act), every employer must provide a workplace 'free from recognized hazards that are causing or are likely to cause death or serious physical harm.' Excessive heat is a recognized hazard. That is the legal hook OSHA already uses to cite employers for heat-related incidents, even without a specific heat standard on the books.
In practice, this means employers are expected to identify heat hazards in their workplace, take reasonable steps to control them, and respond appropriately when workers show signs of heat illness. OSHA's National Emphasis Program on heat, active since 2022, directs inspectors to prioritize workplaces where heat is a known risk — and to look for evidence of a written plan, training, water, rest breaks and a response procedure.
The practical baseline
OSHA guidance treats a heat index of around 80°F as the point where prevention measures should begin — provide cool water, encourage breaks, watch for symptoms and start acclimatizing new workers. Around 90°F, protections should intensify: scheduled paid rest breaks, buddy systems, and active monitoring of anyone doing physical work. These thresholds apply indoors as well as outdoors.
The proposed OSHA heat rule (2026)
OSHA is advancing a proposed federal standard on heat injury and illness prevention that would apply to both indoor and outdoor workplaces. If finalized in its current form, it would establish two clear triggers based on heat index: an 'initial' trigger around 80°F where basic protections apply, and a 'high' trigger around 90°F where enhanced protections apply.
At the initial trigger, employers would generally need to provide cool drinking water, paid rest breaks as needed, access to a cool-down area, and a written heat illness prevention plan. At the high trigger, employers would add scheduled paid rest breaks (typically 15 minutes every two hours), regular check-ins with new or unacclimatized workers, and clear emergency response procedures.
The rule would also formalize a 7 to 14 day acclimatization protocol for new hires and employees returning after time away, along with mandatory supervisor and worker training. Nothing in the proposal is exotic — it codifies what careful employers already do. The value of preparing now is that when the rule becomes final, your business is already operating close to the standard.
Indoor vs outdoor heat exposure
Outdoor heat gets most of the attention, but indoor heat is often more dangerous precisely because it feels routine. There is no sun, no obvious weather event, and staff may not think of a hot warehouse or kitchen as a heat exposure at all. The heat index inside a metal-roofed warehouse in July can exceed the outside temperature by 10 to 20 degrees, especially in the afternoon.
Under the proposed rule and OSHA's current guidance, indoor and outdoor workplaces are treated as sharing the same underlying hazard. What differs is the control strategy: outdoor teams need shade, sun exposure planning and hydration; indoor teams need airflow, spot cooling, break rooms that are meaningfully cooler than the work floor, and attention to heat-generating equipment.
Which businesses are most affected?
Certain business types face indoor heat exposure almost every summer. The tone here is not alarm — it is planning. If you own or manage one of the following operations, indoor heat readiness deserves a place on your annual calendar alongside insurance renewals and tax deadlines.
Warehouses and distribution centers
Large, high-ceilinged spaces with limited air conditioning routinely reach dangerous heat index levels between June and September. Loading docks, upper mezzanines and pick paths near exterior walls tend to be the hottest. Fans alone are not a control above about 95°F — they move hot air without cooling it.
Manufacturing and production floors
Ovens, dryers, motors, welding stations and packaging machines add heat to the space in addition to outdoor conditions. Workers in PPE (gloves, sleeves, aprons, respirators) trap that heat close to the body. Rotation, spot cooling and staged breaks matter more than raising the thermostat.
Restaurants and commercial kitchens
Line cooks, dishwashers and prep staff face some of the highest sustained heat exposures of any indoor role. Ventilation is the single biggest lever, followed by scheduled breaks and cold water access on the line — not just in the break room.
Retail and grocery
Front-of-house may be air conditioned, but stockrooms, receiving areas and rooftop deliveries often are not. Retail owners are frequently surprised by how quickly a stockroom heats up during a heatwave, and how much of a shift some employees spend there.
Offices
Traditional offices rarely reach dangerous temperatures, but HVAC failures during heatwaves — increasingly common as grids strain — can push indoor conditions well past OSHA's comfort range within hours. A short, written response plan for HVAC outages belongs in every office manager's playbook.
Common employer responsibilities
Regardless of whether the federal rule is final in your state yet, the practical responsibilities of a careful employer are already well established. Most of them cost very little to implement and pay for themselves in reduced sick days, fewer errors and lower turnover.
Provide cool drinking water
Cool water — not warm — should be within easy reach of every work area, not just the break room. Plan for at least one quart per employee per hour during heat exposure and assign someone to check and refill stations during the shift.
Schedule breaks and cool-down areas
At sustained heat, breaks work best when they are scheduled and paid, not left to individual discretion. A cool-down area — even a small air-conditioned room or a shaded outdoor space — should be meaningfully cooler than the work area.
Acclimatize new and returning workers
Most serious heat incidents happen in a worker's first two weeks on the job or first days back after time away. A gradual 7 to 14 day ramp-up in workload and heat exposure prevents the majority of these cases.
Train supervisors and staff
Everyone on shift should recognize the difference between heat exhaustion and heat stroke, know when to call 911, and know who is authorized to call a break or stop work. Written records of training — date, topics, attendees — matter if an incident occurs.
Write it down
A short, site-specific written heat plan is the single best defense in an inspection or after an incident. It does not need to be long — a one to three page document that names your triggers, your controls, your emergency procedure and your responsible manager is far more useful than a generic binder.
Common misconceptions
A few beliefs about OSHA and indoor heat come up constantly. Clearing them up saves owners from over-reacting in one direction or under-reacting in the other.
'There is no rule, so I am fine.'
The absence of a specific temperature limit does not remove the employer's duty. OSHA has cited and fined employers for indoor heat incidents under the General Duty Clause for years. A serious incident with no written plan and no training is a difficult situation to defend.
'If I install fans, I am covered.'
Fans help below roughly 95°F by increasing evaporative cooling. Above that, they can actually worsen heat stress by moving hot air across the skin. Fans are one control, not the control.
'My staff can just tell me if they need a break.'
Self-reporting fails predictably in hot conditions. Workers under-report symptoms, especially newer employees who do not want to appear weak. Scheduled breaks at defined triggers are the standard.
'This only matters for outdoor work.'
Indoor heat is the fastest-growing area of OSHA heat enforcement. Warehousing and food service in particular have been high-focus industries under the National Emphasis Program.
Practical actions you can take this week
You do not need a consultant or a large budget to move your business forward on this. The steps below can be completed by a single owner-manager in a few afternoons and will put you ahead of most small businesses in your area.
For a structured, guided version of these steps tailored to your business, our Heatwave Readiness Assessment walks you through the same categories with a written report at the end.
Simple heat readiness checklist
Actionable steps employers can implement immediately.
- Measure the actual temperature and humidity at your hottest work area on a hot afternoon — not the office thermostat.
- Write a one-page heat plan naming your triggers (around 80°F and 90°F heat index), your breaks, your water, and your emergency contact.
- Place cool drinking water within easy reach of every work area, not only in the break room.
- Designate a cool-down area meaningfully cooler than the work floor and confirm it is available all shift.
- Set a 7 to 14 day acclimatization schedule for new hires and anyone returning after two or more weeks away.
- Train supervisors and staff on the signs of heat exhaustion and heat stroke, and post a one-page emergency procedure where they work.
- Review your HVAC service schedule and have a written backup plan for a hot-day HVAC outage.
- Log daily temperature or heat index readings during heat season — a phone photo of a hygrometer counts.
- Set a calendar reminder in early spring each year to review and update the plan before the first hot stretch.
Common mistakes
Waiting for the federal rule to be final
The controls in the proposed rule are already best practice. Employers who wait tend to be the ones caught unprepared when the first heatwave arrives.
Assuming indoor equals safe
Warehouses, kitchens and stockrooms regularly exceed outdoor temperatures on hot days. Indoor exposure is where most small-business gaps sit.
Relying on the thermostat reading
The temperature at the office thermostat is rarely the temperature at the work area. Measure where people actually work, on a hot day, in the afternoon.
No written plan
A verbal understanding does not survive a staff change, an inspection, or an incident. A short written plan is the single highest-leverage step.
Skipping acclimatization
New and returning workers are the most likely to be hurt. A gradual ramp-up in their first two weeks prevents most serious cases.
Frequently asked questions
- Does OSHA require air conditioning?
- No. OSHA does not require air conditioning for most workplaces. Employers are required to control heat hazards using whatever combination of engineering controls, work practices and administrative measures is effective — that may include air conditioning, but it may also include ventilation, spot cooling, shift scheduling, breaks and hydration.
- Is there a legal maximum workplace temperature in the United States?
- No federal law sets a single maximum indoor workplace temperature. OSHA recommends offices stay between roughly 68°F and 76°F for comfort, and treats heat index readings above about 80°F as the point where heat illness prevention should begin. A proposed federal heat rule would formalize specific action triggers for indoor and outdoor work.
- Can employees refuse to work in unsafe heat conditions?
- Employees have a right, under OSHA, to refuse work they reasonably believe presents an imminent risk of death or serious injury when the employer has not corrected the hazard. In practice, most heat situations are resolved by adjusting breaks, hydration and pace before it reaches that point. Retaliating against an employee for raising a safety concern is prohibited.
- What temperature is considered dangerous in a workplace?
- OSHA guidance treats a heat index around 80°F as the point where prevention measures should start and around 90°F as the point where enhanced protections apply, including scheduled paid breaks and active monitoring. The exact temperature that becomes dangerous also depends on humidity, physical exertion, PPE and how acclimatized the workers are.
- What should employers provide during a heatwave?
- At a minimum: cool drinking water within easy reach of every work area, a cool-down area meaningfully cooler than the work floor, scheduled paid rest breaks, extra check-ins with new and returning workers, and a clear written response procedure for symptoms of heat illness. A short written heat plan and trained supervisors tie all of these together.
Author
WorkplaceReady Editorial Team
WorkplaceReady publishes practical, OSHA-aligned guidance on workplace heat safety, risk assessment, and emergency response — written for the people responsible for keeping workers safe.