Seyfarth Synopsis: On August 14, 2026, Cal/OSHA released a revised discussion draft of proposed changes to California’s heat illness prevention standards, Section 3395 (Outdoor Heat Illness Prevention) and Section 3396 (Indoor Heat Illness Prevention). The proposal continues Cal/OSHA’s effort to implement Assembly Bill 2243 while making California’s indoor and outdoor heat standards more consistent in structure and terminology. Although many of the revisions are intended to harmonize the two standards, the draft also contains substantive changes that could significantly affect compliance obligations, including an expansion of outdoor high-heat procedures and new acclimatization requirements for newly-assigned and returning employees. Comments on the discussion draft are due September 21, 2026.
Background
As we previously discussed, Cal/OSHA released proposed revisions to California’s heat illness prevention regulations in May 2025 as part of its effort to implement Assembly Bill 2243. Among other things, the AB 2243 directed Cal/OSHA to consider revisions relating to heat illness prevention plans and acclimatization requirements. Although AB 2243 focused primarily on the outdoor heat standard, Cal/OSHA elected to review both the outdoor and indoor regulations. Following stakeholder comments and advisory committee discussions, Cal/OSHA released a substantially revised draft on August 14, 2026.
Expansion of Outdoor High-Heat Procedures
Perhaps the most consequential proposal in the August draft is the elimination of an existing limitation on Section 3395’s outdoor high-heat procedures, which currently limits the provisions to employers in specified industries, including agriculture, construction, landscaping, oil and gas extraction, and certain transportation operations. The August proposal would remove that industry-based limitation, extending high-heat requirements to a much broader range of outdoor employers whenever temperatures reach 95 degrees Fahrenheit. For employers previously not subject to California’s high-heat requirements, this change could have a significant practical impact.
Expanded Acclimatization Requirements
The August proposal adds more well-defined acclimatization requirements. Under California’s current regulations, employers must closely observe newly assigned employees during specified periods of elevated heat exposure. The August draft would retain and expand concepts first introduced in the May 2025 proposal by addressing both newly assigned employees and employees returning to work after an absence exceeding fourteen days.
Under the proposal, employers would have two options when assigning unacclimatized employees to covered heat conditions. Employers could either implement enhanced protective measures and close observation procedures or phase employees into heat exposure through prescribed exposure schedules. The proposed changes mirror acclimatization provisions in Oregon’s heat illness rule as well as federal OSHA’s proposed heat illness rule.
Although the precise details may continue to evolve during the rulemaking process, the broader message from Cal/OSHA is clear: employers should anticipate greater scrutiny of acclimatization practices.
Distribution of Heat Illness Prevention Plans
The August draft retains one of the most notable additions from the May 2025 proposal: affirmative requirements for distributing Heat Illness Prevention Plans (HIPPs).
Under the proposed language, employers would be required to distribute HIPPs to employees upon hire, during heat illness prevention training, and at least once annually. The proposal clarifies that employers would not be required to distribute the plan to the same employee more than twice each year and would permit electronic posting and distribution in certain circumstances.
Increased Focus on Heat Illness Recognition
The August draft also continues Cal/OSHA’s effort to align definitions and terminology between the indoor and outdoor standards. Among other changes, the proposal would expressly include rhabdomyolysis within the definition of heat illness, add supplements and recreational drugs to the list of personal risk factors, and create a more detailed and consistent description of heat illness signs and symptoms across both regulations. Although these revisions may not dramatically alter day-to-day compliance obligations, employers may ultimately need to update training materials, written programs, and educational resources if the proposal moves forward substantially as drafted.
What Happens Next?
The August 14 proposal remains a discussion draft rather than a formal rulemaking proposal. Additional revisions may occur following the public comment period before Cal/OSHA initiates formal rulemaking under California’s Administrative Procedure Act. Interested stakeholders have until September 21, 2026, to submit comments.
Employer Takeaways
First, the proposal would significantly expand the reach of outdoor high-heat procedures by removing an existing industry-based limitation. Second, Cal/OSHA proposes more well-defined acclimatization requirements for newly assigned and returning employees. Third, employers should anticipate additional administrative obligations relating to Heat Illness Prevention Plan distribution and updates to training materials and written programs.
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