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Walter Reed National Military Medical Center

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Walter Reed National Military Medical Center > wbgt
Heat Cat. WBGT Index, F° Easy Work Moderate Work Hard Work
Work / Rest
Water Intake (Qt/H)
Work / Rest
Water Intake (Qt/H)
Work / Rest
Water Intake (Qt/H)
1 78°F - 81.9°F NL 1/2 NL 3/4 40/20 min 3/4
2 82°F - 84.9°F NL 1/2 50/10 min 3/4 30/30 min 1
3 85°F - 87.9°F NL 3/4 40/20 min 3/4 30/30 min 1
4 88°F - 89.9°F NL 3/4 30/30 min 3/4 20/40 min 1
5 >90°F 50/10 min 1 20/40 min 1 10/50 min 1
** CAUTION: Hourly fluid intake should not exceed 1.5 quarts. Daily fluid intake should not exceed 12 quarts.
  • The work-rest times and fluid replacement volumes will sustain performance and hydration for at least 4 hours of work in the specified heat category. Fluid needs can vary based on individual differences. (plus or minus .25 quart per hour) and exposure to full sun or full shade (plus or minus .25 quart per hour).
  • NL = No limit to work time per hour.
  • Rest means minimal physical activity (sitting or standing), accomplished in shade if possible.
  • Caution: Hourly fluid intake should not exceed 1.5 quarts.
  • If wearing body armor add 5°F to WBGT in humid climates.
  • If wearing NBC clothing (MOPP 4) add 10°F to WBGT.


WBGT As A Guide In Regulating Intensity Of Physical Exertion In Hot Weather

Flag Color

WGBT Index (F)

Intensity of Physical Exercise

<= 81.9

No flag condition.

Green Flag

82 – 84.9

 

 

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

Yellow Flag

85 – 87.9

 

 

Strenuous exercise and activity (e.g. close order drill) should be curtailed for new and unaclimated personnel during the first 3 weeks of heat exposure.

Red Flag 

88 – 89.9

 

 

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

Black Flag

90 and Above

 

 

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

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