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Ready Marine Corps

Emergency Preparedness Program

Brought to You By Your Marine Corps Emergency Management Team
Flag Conditions
The Wet Bulb, Globe Temperature (WBGT) Index is the most effective means of assessing the effect of heat stress on the human 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 Definitions

 Flag Color

 WGBT Index (F)

 Intensity of Physical Exercise


 Less than 80

Extremely intense physical exertion may precipitate heat exhaustion or heat stroke, therefore, caution should be taken.


80 – 84.9

Discretion required in planning heavy exercise for unseasoned personnel. This is a marginal heat stress limit for all personnel.


85 – 87.9

Strenuous exercise and activity (e.g. close order drill) should be curtailed for new and unacclimated personnel during the first three weeks of heat exposure.

 Red 88 – 89.9 

Strenuous exercise curtailed for all personnel with less than 12 weeks training in hot weather.

 Black 90 and Above 

Physical training and strenuous exercise suspended for all personnel (excluding operational commitment not for training purposes).

Note: Wearing of body armor or NBC uniform adds approximately 10 points to the measured WBGT index. Exposure limits should be adjusted accordingly.

  • Flag conditions are monitored from May 1 to Sept. 30, and any other day the temperature could hit 80 degrees.
  • There is one flag condition that’s determined by commanders, rather than the WBGT — “admin black.”

Set your own course through any hazard: stay informed, make a plan, build a kit.
Live Ready Marine Corps.

Where to Find Additional Information

Camp Lejeune Automated Heat Stress System— https://ahss.lejeune.usmc.mil/
Learn about conditions in Camp Lejeune’s mainside, Stone Bay, Courthouse Bay, Camp Geiger and Camp Johnson.

U. S. Naval Hospital Okinawa Online Flag Conditions


Downloadable PDF