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How the Navy's color-coded flag system keeps sailors safe: 'Make sure people are paying attention'

Flag colors change based on the temperature
Navy heat flag levels
Posted at 12:18 PM, Jul 28, 2021
and last updated 2021-07-28 12:18:16-04

NORFOLK, Va. -- Physical fitness is a big component of service in the Navy, but staying safe when exercising during the hot and humid summer months is a top priority.

The Navy invited WTKR anchor Todd Corillo to see the color-coded flag system in use outside the NH-30 gym at Naval Support Activity Hampton Roads.

On a pole outside the main gym entrance, the Navy hangs one of five different flags depending on the conditions.

Fitness Specialist Matt Smith and coworkers check the outdoor temperature hourly using a WetBulb Globe detector.

According to the National Weather Service, WetBulb Globe Temperature "is a measure of the heat stress in direct sunlight, which takes into account: temperature, humidity, wind speed, sun angle and cloud cover."

That differs from heat index which is calculated for shady areas.

Once a temperature is recorded, the appropriate flag color - blue, green, yellow, red or black - is then hung based on the WetBulb Globe Temperature chart.

A blue flag is the lowest intensity level, while a black flag indicates the most dangerous physical exertion conditions above 90 degrees Fahrenheit.

"Almost every day last week was a black flag situation," Smith told Corillo.

"We have to make sure that people are paying attention to how hot it's going to be," he added.

Fitness staff encourage folks to consider an indoor exercise on days where the temperature gets hot and remind them to stay hydrated and take frequent breaks.