Marines Overhaul Heat and Cold Injury Guidance After 11 Years and WBGT Takes Center Stage

The Marine Corps has issued updated interim guidance on preventing heat and cold weather injuries, marking the first revision to its extreme weather safety policy in eleven years. The new directive pushes commanders and officers in charge to expand training, formalize response plans, and build standard operating procedures for training and operations conducted in hot and cold environments alike.

The guidance is labeled “interim” because it hasn't yet been folded into the Marine Corps Safety Management System, but it is in effect now and will remain so until formally adopted or replaced. Given how long the previous policy had gone unrevised, that interim status hasn't slowed its rollout across the force.

What the Updated Guidance Requires

Commanders must ensure Marines receive training on the causes, prevention, and treatment of heat and cold stress injuries. That training now specifically includes work-rest cycles, heat flag warning systems, the Wet Bulb Globe Temperature (WBGT) index, and the wind chill index. Medical personnel assigned to units are required to maintain rapid response plans and designated cooling or warming areas, and troops showing signs of excessive heat stress may need evaluation by a qualified health care provider to determine whether an injury actually occurred.

The guidance also adds a reporting requirement: unit safety representatives must log all confirmed heat or cold injuries into the Risk Management System, creating a more consistent, trackable record across the service than existed under the old policy.

Why WBGT Gets Top Billing

Notably, the guidance places specific emphasis on the WBGT index over the more familiar heat index. A standard heat index only accounts for air temperature and humidity. WBGT goes further, factoring in direct sunlight, wind speed, sun angle, and cloud cover, which makes it a far more complete picture of the heat stress a body actually experiences during physical exertion outdoors. That distinction matters most for exactly the kind of activity Marines train for: sustained, high-intensity work in full gear, often in direct sun, with no option to simply stop for the day when conditions turn dangerous.

This mirrors a broader shift happening well beyond the military. Athletic trainers, OSHA compliance officers, and safety professionals across construction, agriculture, and manufacturing have all moved toward WBGT-based decision-making for the same reason: it reflects actual environmental conditions instead of a general approximation, giving leaders an objective trigger for adjusting work-rest cycles instead of relying on a subjective read of how hot it feels standing in the shade.

The Numbers Behind the Update

The timing lines up with troubling injury data. According to a Military Health System report, service members across all branches experienced 2,751 heat-related injuries in 2025, with the Marine Corps accounting for 641 of them. That's actually a decrease from 655 cases the year before, but still a substantial toll across the force. Cold weather injuries told a similar story: the Marine Corps reported 107 cases, the second-highest total behind the Army, including 40 cases of non-freezing peripheral injury (commonly known as trench foot), 49 cases of frostbite, and 18 cases of hypothermia.

Those figures underscore why the update was overdue. Eleven years is a long stretch without revisiting safety guidance, especially as environmental extremes on both ends of the thermometer have grown more frequent and more severe across nearly every region where Marines train and deploy.

The Takeaway for Anyone Managing Heat Risk

Whether you're a battalion safety officer or a civilian safety manager, the Marine Corps' updated approach offers a useful blueprint: train people on the specific hazard, standardize the measurement used to make decisions, build response and reporting plans before an incident happens, and make evaluation by qualified personnel a routine part of the process rather than an afterthought.

WBGT-based decision-making sits at the center of that approach for a reason. It's the measurement that most closely reflects what a body is actually experiencing in the field, which is exactly why it continues to become the standard across military, athletic, and occupational heat safety programs alike — and why accurate, on-site WBGT monitoring is becoming less of a specialty tool and more of a baseline expectation everywhere heat is a genuine operational risk.

Frequently Asked Questions

What changed in the Marine Corps' new heat and cold injury guidance?

It's the first update in 11 years, and it requires commanders to expand training on heat and cold stress injuries, build standard operating procedures for extreme weather operations, and log all confirmed injuries in the Risk Management System.

Frequently Asked Questions

Why does the guidance emphasize WBGT over the standard heat index?

WBGT accounts for direct sunlight, wind speed, sun angle, and cloud cover in addition to temperature and humidity, making it a more accurate measure of real heat stress during physical exertion outdoors than the heat index alone.

Frequently Asked Questions

How many heat-related injuries did the Marine Corps report in 2025?

The Marine Corps reported 641 heat-related injuries in 2025, down from 655 the year before, out of 2,751 total heat-related injuries across all military branches.

Sources:

Marine Corps Times, “Marines release updated heat, cold injury safety guidance,” July 22, 2026; Marine Corps Heat and Cold Stress Injury Prevention Program guidance; Military Health System Monthly Surveillance Report, May 2026.