What OSHA requires for heat in 2026
As of 2026 there is no final federal OSHA heat standard. Federal OSHA enforces heat hazards under the General Duty Clause, OSH Act Section 5(a)(1) (29 U.S.C. 654(a)(1)) 29 U.S.C. 654(a)(1), backed by the OSHA Heat National Emphasis Program (NEP). OSHA also publishes a Model Heat Illness Prevention Plan and the “Water. Rest. Shade.” campaign. A proposed rule (NPRM — 89 FR 70698 (Aug 30, 2024)) would create the first dedicated heat standard, with parallel construction (29 CFR 1926) provisions — but it is not in force: Post-hearing phase as of mid-2026; no final rule published. Retained (not withdrawn) on the Sept 2025 Unified Regulatory Agenda.
Practically, an employer can still be cited today for a recognized heat hazard. The fastest way to show you took reasonable steps is a written plan covering the five OSHA pillars: water, rest, shade, acclimatization, and training/emergency response — exactly what the builder above generates.
OSHA heat-index risk bands and required actions
Use the heat index (apparent temperature from air temperature and humidity), not the raw thermometer reading. OSHA's “Using the Heat Index” guidance maps the heat index to four risk bands, each with an escalating action set:
| Risk band | Heat index | Risk tier | Required actions |
|---|---|---|---|
| Lower (Caution) | Below 91°F | Lower | Basic heat safety: provide water, allow rest in shade, train workers on heat-illness signs. |
| Moderate | 91–103°F | Moderate | Increase rest breaks, ensure shade and cool water are readily available, actively monitor workers, acclimatize new/returning workers. |
| High | 103–115°F | High | Add rest periods and/or reduce work intensity, consider physiological monitoring, ensure trained supervision, confirm first-aid and emergency procedures. |
| Very High to Extreme | 115°F and above | High (Extreme) | Reschedule non-essential work, use the most aggressive controls, and treat any symptom as an emergency. |
Source: OSHA “Using the Heat Index: A Guide for Employers” (campaign guidance, not a codified standard).
Water, rest, shade & acclimatization at a glance
| Control | What to do | Source |
|---|---|---|
| Water | ≥ 1 cup (8 oz) cool water every 20 min (~32 oz/hr); electrolytes for jobs over 2 hours. | OSHA Water. Rest. Shade. |
| Rest & shade | Break length/frequency rise with heat stress; provide a cool recovery location (shade or A/C). | OSHA heat guidance |
| Acclimatization (new workers) | Build to full exposure over 7–14 days; ~20% of shift on day 1. | NIOSH / OSHA |
| Re-acclimatization | After a week+ away from heat, allow 2–3 days to re-adapt. | NIOSH / Cal/OSHA |
The proposed federal heat rule (what is coming)
OSHA's proposed rule, Heat Injury and Illness Prevention in Outdoor and Indoor Work Settings (NPRM — 89 FR 70698 (Aug 30, 2024)), would set two heat-index triggers and minimum controls:
- Initial heat trigger — 80°F heat index: cool drinking water at 1 quart per hour per employee, access to shade/break areas, and a written plan.
- High-heat trigger — 90°F heat index: mandatory paid rest breaks of 15 minutes at least every 2 hours, plus a buddy/observation system.
- Construction is covered by parallel 29 CFR 1926 provisions in the same proposal.
These figures are proposed, not in force. Building to them now future-proofs your program.
Worked examples
Example 1 — 95°F air, 55% humidity. The NWS heat index is about 109°F, which falls in OSHA's High band (103–115°F). The plan calls for added rest periods and/or reduced work intensity, trained supervision, water on a 20-minute schedule, electrolytes for shifts over two hours, and ready first-aid/emergency procedures.
Example 2 — 88°F air, 40% humidity. The heat index is about 88°F (Lower/Caution band, below 91°F). Basic precautions apply: provide and encourage water, allow rest in shade, and train workers on the signs of heat illness. New or returning workers should still be acclimatized over 7–14 days, since most fatalities occur in a worker's first days.
What to do next
- Build and post a written plan. Use the builder above, add your supervisor and nearest medical facility, and download the PDF. Keep it on the jobsite and review it in toolbox talks.
- Acclimatize new and returning workers. Start at ~20% of the shift and build over 7–14 days; the first few days are the most dangerous.
- Check the heat index daily, not just the temperature, and step up controls as the band rises.
- Train for emergencies. Everyone should know heat-stroke signs, that 911 comes first, and how to cool a worker aggressively while waiting for help.
- Confirm your state's rules. State-plan states — the 22 with a full plan covering private employers, plus 7 covering public employees only — set their own standards, and several have adopted heat rules that go beyond federal guidance: California (8 CCR 3395 (Cal/OSHA)), Oregon, Washington and Nevada among them. A state without a plan can still regulate heat through other state law, so check your own state as well as OSHA.
Frequently asked questions
Does OSHA require a written heat illness prevention plan in 2026?
There is no final federal OSHA heat standard as of 2026, so federal OSHA does not yet mandate a written plan for every employer. Federal OSHA publishes a Model Heat Illness Prevention Plan and enforces heat hazards under the General Duty Clause, Section 5(a)(1) of the OSH Act, plus its Heat National Emphasis Program. Several state plans go further: Cal/OSHA (8 CCR 3395) requires a written plan for outdoor heat, and Oregon, Washington, Nevada, Maryland and Minnesota have their own heat rules. Colorado is not a state-plan state — its heat protections come from state labor law rather than an OSHA-approved plan, so check your own state's rules whether or not it runs a plan. A written plan is the single strongest way to show good faith if you are inspected.
What temperature triggers heat illness prevention requirements?
OSHA's "Using the Heat Index" guidance uses heat-index bands rather than a single number: Caution below 91°F, Moderate 91–103°F, High 103–115°F, and Very High to Extreme at 115°F and above. The proposed federal heat rule (89 FR 70698, not finalized) would set an initial heat trigger at an 80°F heat index and a high-heat trigger at 90°F. Cal/OSHA's codified outdoor trigger is 80°F air temperature. Use the heat index, not the raw thermometer reading, because humidity sharply raises the real heat load on the body.
How much water should workers drink in the heat?
OSHA recommends at least one cup (8 oz) of cool water every 20 minutes while working in the heat — roughly four cups (32 oz) per hour. Workers should drink on a schedule and not wait until they feel thirsty. For jobs lasting more than two hours, provide electrolyte-containing beverages in addition to water, because sweating loses electrolytes that plain water cannot replace. The proposed federal rule would require cool drinking water at 1 quart per hour per employee.
How long does heat acclimatization take?
Acclimatization typically peaks within 4–14 days of regular work for at least two hours per day in the heat. NIOSH and OSHA recommend gradually building exposure — for example, about 20% of a normal shift on day one for new workers, increasing each day. After a week or more away from the heat (vacation, illness, weather), workers usually need 2–3 days to re-acclimatize. Most heat-illness fatalities happen in a worker's first few days on the job, which is why acclimatization is the highest-leverage control.
What should I do if a worker shows signs of heat stroke?
Heat stroke is a medical emergency — call 911 immediately. When confusion, slurred speech, or unconsciousness are present, treat it as heat stroke. Move the worker to a cooler area and cool them aggressively: cold-water or ice-bath immersion is the most effective method; otherwise place ice or cold wet towels on the head, neck, trunk, armpits, and groin and use fans. Do not leave the worker alone, and do not give fluids by mouth if the worker is confused or unconscious. Cooling first, then transport — minutes matter.
What is the difference between heat exhaustion and heat stroke?
Heat exhaustion is the earlier, treatable stage: fatigue, heavy sweating, dizziness, nausea, headache, and an elevated body temperature or fast heart rate. The worker is still alert. Heat stroke is the life-threatening stage: the body's temperature regulation fails, producing very high body temperature with confusion, slurred speech, seizures, or unconsciousness. Heat exhaustion can progress to heat stroke if ignored, so cool and rest a worker at the first signs rather than waiting.
Is this heat illness prevention plan builder free?
Yes. The builder, the live heat-index calculator, and the downloadable PDF plan are completely free with no login. The plan content is verified against OSHA's heat pages, the OSHA Model Heat Illness Prevention Plan, and NIOSH guidance. It is general information to help you build a plan — it is not legal or medical advice, and in an emergency you should call 911.
Sources & verification
- https://www.govinfo.gov/content/pkg/FR-2024-08-30/html/2024-14824.htm
- https://www.osha.gov/heat-exposure/rulemaking
- https://www.federalregister.gov/documents/2024/08/30/2024-14824/heat-injury-and-illness-prevention-in-outdoor-and-indoor-work-settings
- https://www.osha.gov/heat-exposure/standards
- https://www.osha.gov/heat-exposure/water-rest-shade
- OSHA Model Heat Illness Prevention Plan (2021) and OSHA “Heat-Related Illnesses and First Aid”.
- NIOSH Criteria for a Recommended Standard: Occupational Exposure to Heat and Hot Environments.
- NWS heat index (Rothfusz regression) — wpc.ncep.noaa.gov/html/heatindex_equation.shtml.
Heat facts verified 2026-08-21. This tool provides general information and is not legal or medical advice. In an emergency, call 911. Heat hazards may still be cited under the General Duty Clause even without a final heat standard — and an uncorrected violation can run up to $16,550/day in failure-to-abate penalties.
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