Automated Heat Stress System

The Automated Heat Stress System (AHSS) system is active. Please visit this page for real-time AHSS updates.

See the Ministry of the Enviroment website for the Heat Stress Index in Iwakuni and refer to the corresponding flag conditions below.

Click for Hourly Heat Stress Index

Flag Condtions

The Wet Bulb, Globe Temperature (WBGT) Index is the most effective means of assessing the effect of heat stress on the human body. It does not reflect the ambient temperature, it reflects the heat stress condition that effects your body. The WBGT Index is used to determine Flag Conditions as a safety standard for how long individuals can safely work out of doors in hot humid conditions. Knowing and understanding these Flag Conditions will help keep you safe from heat-related emergencies like heat cramps, heat exhaustion, and heat/sun stroke. Color coded flags are flown in strategic locations on Marine Corps Installations to communicate hazardous conditions to personnel so that work and outdoor activity can be adjusted accordingly.

Color Defintions

Green, WBGT Index (°F): 80 – 84.9
Unacclimated personnel must perform heavy exercises with caution and under constant supervision. Organized PT evolutions in boots and utilities are allowed for all personnel.

Yellow, WBGT Index (°F): 85 – 87.9
Strenuous exercise and activity ( e.g., close order drill) should be curtailed for new and unacclimated personnel during the first 3 weeks of heat exposure.

Red, WBGT Index (°F): 88 – 89.9
Strenuous exercise curtailed for all personnel with less then 12 weeks training in hot weather. Troops who are thoroughly acclimated may perform limited activity not to exceed 6 hours a day.

Black, WBGT Index (°F): 90 and Above
Physical training and strenuous exercise suspended for all personnel (excludes operational commitment not for training purposes).


For questions about the Heat Stress Flag Condition in your local area, please contact the appropriate office below:

  DSN Off-Base
MCAS Iwakuni, Duty Officer 253-4401 0827-79-4401
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