Heat Illness Prevention Plan: What a Written HIIPP Must Include

A Heat Illness Prevention Plan (HIIPP) is the written document that shows you addressed heat as a recognized hazard. As of 2026 there is no final federal heat standard (only a proposed rule, NPRM 89 FR 70698, Aug 30, 2024), so heat is enforced under the General Duty Clause, 29 U.S.C. 654(a)(1). A complete HIIPP must cover six elements: water, shade/rest, acclimatization, monitoring, training, and emergency response. This guide is about the plan itself — what goes in each section, who owns it, and the gaps that get crews cited.

For the rulemaking status and timeline, see Is There an OSHA Heat Standard Yet?. For the day-by-day ramp-up, see the 7-14 day acclimatization protocol. This post focuses on building and documenting the written plan.

Why a Written Plan, When There's No Final Rule

It is tempting to wait for the final federal rule. That is a mistake, for three reasons:

1. Heat is already enforceable. OSHA cites heat under the General Duty Clause (Section 5(a)(1)) and runs a national Heat National Emphasis Program that actively targets hot-weather inspections. To sustain a citation, OSHA shows the hazard existed, was recognized, was likely to cause serious harm, and that a feasible abatement existed. Heat illness is textbook "recognized," so the only real question on inspection is what did you do about it. A written plan is your answer.
2. Some states already require the document. State Plans must be at least as effective as federal OSHA (29 CFR 1902.3(c)(1)) and may exceed it. California's 8 CCR 3395(i) requires a written heat illness prevention plan for outdoor workplaces, in English and in the language most of the workers understand, and 3395(d)(1) requires shade once the temperature exceeds 80°F. That is in force today, not proposed.
3. The penalties are real. A serious General Duty Clause citation can reach $16,550; a willful or repeat citation up to $165,514 (29 CFR 1903.15(d)(1) to (d)(3)). A complete plan with training records addresses both the citation risk and the underlying injury.

The 80°F and 90°F Proposed Triggers

OSHA's proposed rule (89 FR 70698) would add 29 CFR 1910.148, and 29 CFR 1926.67 would apply it to construction. It sets two heat-index triggers. They are proposed, not in force, but they give a concrete outline for a plan.

Heat index, not air temperature. The trigger is the heat index (temperature plus humidity), not the thermometer reading in the shade. At 90°F air temperature and 70% humidity the heat index is well over 100°F. Direct sun can add up to 15°F, according to the National Weather Service. Your plan should say how you obtain the heat index (the OSHA-NIOSH Heat Safety Tool app, a posted local forecast, or an on-site measurement).

OSHA's legacy "Using the Heat Index" guidance sorts conditions into risk bands — Lower/Caution below 91°F, Moderate 91–103°F, High 103–115°F, and Very High to Extreme at 115°F and above — with escalating protective measures in each. Build those bands into your plan so supervisors know what to do as conditions climb.

The Six Elements of a HIIPP

A plan that says "we provide water and shade" is a paragraph, not a program. The table sets out what each of the six sections should contain. Two pieces already apply on every construction site, heat standard or not: an adequate supply of potable water (29 CFR 1926.51(a)(1)) and instruction in recognizing and avoiding unsafe conditions (29 CFR 1926.21(b)(2)).

Element 3 in one line

OSHA reports that almost half of heat-related deaths occur on a worker's first day on the job or first day back after an extended absence, and over 70% during the first week. The Rule of 20% that OSHA and NIOSH recommend starts new workers at 20% of the normal duration in the heat on day one and adds no more than 20% a day, reaching a full schedule by the end of the first week; some workers need up to 14 days. Workers returning after an absence of a week or more need the same gradual ramp. The proposed rule would make one of two protocols mandatory for a new employee's first week (proposed 29 CFR 1910.148, paragraph (e)(7)(i)). The full schedule is in our acclimatization protocol guide.

Worked Example: From Forecast to a Compliant Shift

A roofing crew of 8 is starting a new tear-off in July. Two workers are new this week.

1. Pre-shift (planning). The foreman checks the heat index forecast: 94°F by 1 p.m. — above the 90°F high-heat trigger. The plan's high-heat provisions are in effect for the day.
2. Water. At 8 workers × ~1 qt/hour over an 8-hour shift, the crew needs ≈16 gallons of cool water staged and a plan to refill it. Coolers go up before work starts.
3. Shade. A pop-up canopy and the air-conditioned truck cab serve as the cool-down area — sized for the whole crew on a staggered break.
4. Acclimatization. The two new workers run the Rule of 20% ramp and are paired with experienced workers; the foreman gives them extra first-week attention.
5. Monitoring. Above 90°F the plan requires a buddy system and a paid 15-minute break roughly every 2 hours in the shade.
6. Emergency readiness. The plan's emergency card — site address, gate code, nearest hospital, "cool first, call fast" steps — is posted in the truck and reviewed at the toolbox talk.

Every one of those steps maps to a written section of the HIIPP. That traceability is what lets you show the plan was carried out.

Documentation: What to Keep

A plan only protects you if you can prove it was implemented. Keep:

• The signed, dated written plan on site (and in your safety app), reviewed at least annually and after any serious heat incident, the review cycle in proposed 29 CFR 1910.148, paragraph (c)(7).
• Training rosters — date, topic, trainer, and worker signatures — for workers and supervisors, in the language used.
• Daily high-heat records on triggered days (heat index, breaks taken, water provided, acclimatization status of new workers).
• A named person responsible by title for monitoring and enforcement.
• Injury records. A heat illness that needs medical treatment beyond first aid goes on the OSHA 300 log; drinking fluids for relief of heat stress is first aid (29 CFR 1904.7(b)(5)(ii)(N)). A heat fatality is reported to OSHA within 8 hours and an in-patient hospitalization within 24 hours (29 CFR 1904.39(a)(1) and (a)(2)).

Run the topics through a 5-minute toolbox talk with a sign-in sheet so the training is both delivered and documented.

Common Mistakes to Avoid

• Don't rely on air temperature — the triggers are heat index (temp + humidity + sun).
• Don't ship a generic template with no jobsite specifics (site address, shade location, responsible person).
• Don't omit the acclimatization schedule: over 70% of heat deaths occur in a worker's first week (OSHA).
• Don't train workers but skip supervisors, or train only in English for a bilingual crew.
• Don't write "call 911" without the site address, access details, and active-cooling steps for heat stroke.
• Do assign one person by title to monitor conditions and enforce water/rest.
• Do keep daily records on high-heat days — the plan plus the records is your defense.

Heat Exhaustion vs Heat Stroke (Train Everyone on This)

Heat stroke is life-threatening; minutes of active cooling before EMS arrives save lives. Make this table the centerpiece of your training section. On a construction site, 29 CFR 1926.50(e) already requires equipment for prompt transport of the injured person or a communication system to reach an ambulance, and 29 CFR 1926.50(f) covers posting emergency numbers, or the site location where 911 does not receive it automatically.

What to Do Next

1. Write (or update) your six-element HIIPP and put it on every jobsite.
2. Add a written acclimatization ramp for new and returning workers.
3. Train workers and supervisors and keep signed rosters.
4. Set up daily high-heat recordkeeping before the next heat wave.

Build a jobsite-ready, documented plan in minutes with the Heat Illness Prevention Plan Builder. Then deliver it on site with a toolbox talk, and tie it into your written Emergency Action Plan.

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Sources: OSHA Heat rulemaking and "Water. Rest. Shade." campaign; Heat NPRM 89 FR 70698 (Aug 30, 2024); OSH Act Section 5(a)(1), 29 U.S.C. 654(a)(1); Cal/OSHA 8 CCR 3395; OSHA penalty schedule. Facts verified against the eCFR (current as of September 25, 2026), the proposed rule text, OSHA's Protecting New Workers page and 8 CCR 3395 on October 5, 2026. Heat triggers shown are proposed and not yet enforceable; check your State Plan. This is compliance guidance, not legal advice.

Related: Is There an OSHA Heat Standard Yet? · 7-14 Day Acclimatization Protocol · 5-Minute Toolbox Talks · Heat Illness Prevention Plan Builder