Lack of preparation, you can’t run a marathon if you haven’t been training a few months prior.
Flag Color | WGBT Index (F) | Intensity of Physical Exercise |
White | Less than 80 (27 Celsius) | Extremely intense physical exertion may precipitate heat exhaustion or heat stroke, therefore, caution should be taken. |
Green | 80 – 84.9 (27 - 30 Celsius) | Discretion required in planning heavy exercise for unseasoned personnel. This is a marginal heat stress limit for all personnel. |
Yellow | 85 – 87.9 (30-32 Celsius) | 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 (32-33 Celsius) | Strenuous exercise curtailed for all personnel with less than 12 weeks training in hot weather. |
Black | 90 and Above (33 and over) | Physical training and strenuous exercise suspended for all personnel (excluding operational commitment not for training purposes). |
The leading cause of these training accidents is heat stroke and poor hydration.
Hao instructors should give the recruits sufficient water breaks and limit the training when the sun is hot (black flag days).
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.
Heat Related Emergencies:
- Heat cramps—Muscle spasms and aches from heavy exertion in extreme heat. They are usually the first sign of heat-related complications.
- Heat exhaustion—A form of mild shock that results from insufficient body fluids due to extreme heat and excessive exercising. The blood flow to the skin increases, decreasing blood flow to vital organs and raising the body temperature, increasing the risk of a heat stroke.
- Heat stroke/sun stroke—The body’s temperature control system stops working, causing body temperature to rise so high (103ºF or more) that there may be brain damage or death.
Flag Color WGBT Index (F) Intensity of Physical Exercise
WhiteLess than 80 (27 Celsius) Extremely intense physical exertion may precipitate heat exhaustion or heat stroke, therefore, caution should be taken.
Green80 – 84.9 (27 - 30 Celsius) Discretion required in planning heavy exercise for unseasoned personnel. This is a marginal heat stress limit for all personnel.
Yellow85 – 87.9 (30-32 Celsius) 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.
Red88 – 89.9 (32-33 Celsius) Strenuous exercise curtailed for all personnel with less than 12 weeks training in hot weather.
Black90 and Above (33 and over) Physical training and strenuous exercise suspended for all personnel (excluding operational commitment not for training purposes).