Extreme heat can be very dangerous. In extreme heat and high humidity, evaporation is slowed and the

human body must work extra hard to maintain a normal temperature. This can push the body beyond its

limits. In the United States each year, hundreds of people die from heat-related complications.

Aboard Navy installations, Flag Conditions are used to communicate hazardous heat conditions. It is

important for Navy personnel and families to understand these flag conditions and what each color


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 Naval

Installations to communicate hazardous conditions to personnel so that work and outdoor activity can

be adjusted accordingly.

 White Flag (WGBT Index less than 80° Fahrenheit) — Extremely intense physical exertion may

precipitate heat exhaustion or heat stroke, therefore, caution should be taken.

 Green Flag (WGBT Index 80-84.9° Fahrenheit) — Discretion required in planning heavy exercise

for unseasoned personnel. This is a marginal heat stress limit for all personnel.

 Yellow Flag (WGBT Index 85-87.9° Fahrenheit) — Strenuous exercise and activity (e.g. close

order drill) should be curtailed for new and personnel not acclimated to the heat during the first

three weeks of heat exposure.

 Red Flag (WGBT Index 88-89.9° Fahrenheit) — Strenuous exercise curtailed for all personnel with

less than 12 weeks training in hot weather.

 Black Flag (WGBT Index 90° Fahrenheit and above) — Physical training and strenuous exercise

suspended for all personnel (excluding operational commitment not for training purposes).

How to Prepare For Extreme Heat

Be informed and know heat terminology:

 Heat Wave — An extended period of extreme heat, usually combined with excessive humidity.

 Heat Index — A number of degrees in Fahrenheit (F) added to the air temperature that tells how

hot it feels with the relative humidity.

 Excessive Heat Watch — Conditions are favorable for an excessive heat event to meet or exceed

local Excessive Heat Warning criteria in the next 24 to 72 hours.

 Excessive Heat Warning — Heat Index values are forecast to meet or exceed locally defined

warning criteria for at least two days (daytime highs = 105-110° Fahrenheit).

 Heat Advisory — Heat Index values are forecast to meet locally defined advisory criteria for one

to two days (daytime highs = 100-105° Fahrenheit).

Plan Ahead

 Listen to local weather forecasts and stay aware of upcoming temperature changes.

 Be aware that people living in urban areas may be at greater risk from the effects of a prolonged

heat wave than are people living in rural areas, due to stagnant and poor air quality, as well as

stored heat in asphalt and concrete.

 Make a plan to keep you and your family safe from the effects of extreme heat.

 Make sure you have a fan, snugly fit window air conditioner, or something to circulate air in

extreme heat as many heat-related deaths can be attributed to stagnant atmospheric conditions

or poor air quality.

 Insulate air ducts and weather-strip doors and sills to keep cool air in.

 Cover windows that receive morning or afternoon sun with drapes, shades, awnings, etc.

 Keep storm windows up year round.

 Understand that elderly, young, sick and overweight individuals are at greater risk and learn first

aid to help treat heat related emergencies.

 Build an emergency kit.

What to Do If There Is Extreme Heat

 Slow down and don’t do anything too strenuous.

 Stay inside as much as possible.

 Never leave children or pets alone in closed vehicles.

 If air conditioning is not available in your home, stay on the lowest level or go to a public

building with air conditioning.

 If you stay in your home without air conditioning, make sure there is a way, such as a fan, to

circulate the air around you.

 Drink lots of water, even if you don’t feel thirsty.

 Eat well-balanced, light and regular meals.

 Avoid alcohol, caffeine and salt.

 Wear loose-fitting, lightweight and light-colored clothing.

 Be aware that a power outage or drought can result from a heat wave.

Heat Emergencies

Keep a lookout for possible heat 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 (103° F or more) that there may be brain damage or death.

If you experience or observe any of the above conditions, seek medical attention immediately … and Be

Ready Navy!

Editor’s Note: The content of this article is provided for educational purposes only. The content provided

is not intended to be a substitute for professional medical advice, diagnosis or treatment. Always seek

the advice of your physician or other qualified health professional with any questions you may have

regarding a medical condition.


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