100F + 100%RH == ~195F Heat Index. That is WELL into the Black Flag range. Under a black flag, even the military does restricted work periods if they must be ou

100F + 100%RH == ~195F Heat Index. That is WELL into the Black Flag range. Under a black flag, even the military does restricted work periods if they must be out. > A black flag weather condition is in effect when the temperature reaches 90 degrees or higher, according to the Safety Office's heat stress card. In this category, only 10 minutes out of each hour should be spent engaging in strenuous activities, only 20 minutes should be spent performing moderate work and 50 minutes could be spent doing easy work. Strenuous work includes intense jogging and walking on hard surfaces at 3.5 mph with loads of 40 pounds or more. Moderate work includes performing calisthenics and easy work includes marksmanship training and light walking with no load. Community members should drink one quart of water per hour while performing any type of work while a black flag is raised.