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Updated heat and cold stress injury prevention guidance for commanders

MARADMIN 311/26·July 9, 2026·2 min read·Official source
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The Marine Corps issued new interim guidance on heat and cold stress injury prevention, canceling MARADMIN 111/15. The update clarifies what commanders, supervisors, and installation commanders must do before and during training or operations in hot or cold environments. It stays in effect until it gets folded into MCO 5100.29C or a newer message supersedes it.

Heads up: This replaces 11-year-old guidance. If your unit's SOPs or training materials reference MARADMIN 111/15, they need to be updated.

Who it affects

All commanders and OICs running training or operations. Officers, SNCOs, and NCOs in any supervisory role. Installation, base, and station commanders. Medical department personnel assigned to Marine Corps units. Effectively, anyone responsible for Marines in a field or training environment, which includes reserve units during AT and IDT.

What you need to do

Commanders and OICs:

  1. Build or update your SOP for hot and cold weather training, including how your unit operates and maintains its wet-bulb globe temperature (WBGT) meter.
  2. Train all potentially exposed personnel on heat and cold stress causes, prevention, and treatment. Cover the WBGT index, work/rest cycles, flag warning systems, and wind chill index. Document attendance.
  3. Conduct refresher training before any exposure to hot or cold environments.
  4. Before training or operations: confirm personnel are acclimatized and properly equipped, designate monitors to watch for stragglers and casualties, and notify the supporting military treatment facility (MTF) of your risk assessment, time, and location.
  5. Identify personnel with risk factors (prior heat/cold stress history, medications, supplements). Get them evaluated and cleared by a medical provider, and have supervisors and buddies watch them.
  6. Ensure adequate hydration, rest, and water breaks throughout.
  7. Report all heat or cold injuries through the Risk Management Information (RMI) system and the disease report system internet (DRSi), per the referenced instructions.

Officers, SNCOs, NCOs, and other supervisors:

  • Make sure your Marines and Sailors know heat and cold stress prevention procedures.
  • Push buddy aid. If someone looks sick or off, they go to medical, period.

Installation, base, and station commanders:

  • Operate and maintain WBGT meters per manufacturer guidance.
  • Take readings in operational areas, display flags, and push WBGT index readings and wind chill data to all tenant commands.
  • Provide WBGT loaner equipment to units as needed and maintain SOPs for it.

Key dates

  • Effective now. This MARADMIN was released 8 July 2026.
  • No expiration date stated. Guidance remains in effect until incorporated into MCO 5100.29C or superseded.

The official version

See MARADMIN 311/26 for the full text.

Key references: MCO 5100.29C (Safety Management System), NAVMED P-5010-3 (Heat and Cold Stress Injuries), and BUMEDINST 6220.12D (Medical Surveillance and Response). Links to those documents are not provided here; check with your unit safety officer or S-3.

POC: CDR Linda Sharpe, CMC Washington DC (SD), linda.d.sharpe.mil@usmc.mil, 703-571-6515.

This is written by a reservist, for reservists. It is not an official publication of HQMC or MARFORRES. Always verify guidance with your command or unit S-1 before acting on any article or summary.

Resources & references

The documents this bulletin points to, with a plain-English note on why each matters. Links marked CAC required need a government login.

  • Safety Management System (MCO 5100.29C)Reference

    This is the overarching Marine Corps safety management order. This MARADMIN states that its interim guidance remains in effect until incorporated into this order, making it the governing document for the long term.

  • Risk Management (MCO 5100.29C Vol 2)Reference

    This volume covers risk management principles that commanders and OICs are directed to apply when implementing heat and cold stress injury prevention measures for all operational and training activities. It is also the authority for reporting heat and cold injuries via the RMI system.

  • Manual of Naval Preventive Medicine: Heat and Cold Stress Injuries (NAVMED P-5010-3)Reference

    This Navy Medicine manual covers heat and cold stress injuries for ashore, afloat, and ground forces. Commanders are directed to implement its requirements and use its training guidelines to reduce risk.

  • Manual of Preventive Medicine, Chapter 9, Sections V and VI (Preventive Medicine for Ground Forces)Reference

    This legacy manual chapter provides preventive medicine guidance specifically for ground forces. Commanders are directed to implement its requirements alongside the other medical references.

  • Prevention and Treatment of Heat and Cold Stress Injuries (NMCFHPC-TM 6260.6B)Reference

    This technical manual from Navy Medicine addresses prevention and treatment of heat and cold stress injuries. Commanders are directed to implement its requirements and use it to set WBGT flag display and training guidelines.

  • Navy and Marine Corps Safety Investigation and Reporting Manual (MCO 5100.29C Vol 9)Reference

    This volume governs how safety incidents are investigated and reported. All heat and cold injuries must be reported via the Risk Management Information system per this reference.

  • Medical Surveillance and Response (BUMEDINST 6220.12D)Reference

    This Bureau of Medicine instruction governs medical surveillance and response. All heat and cold injuries must be reported through the disease report system internet per this reference.

  • MARADMIN 111/15 (cancelled by this message)MARADMIN

    This is the previous heat and cold stress injury prevention MARADMIN that this message explicitly cancels and replaces. Reservists should discard it and use the current guidance instead.

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