Flag Alert System

The military and other organizations have systems of colored flags, which indicate the level of danger due to heat stress. The flag threshold temperatures are based on wet bulb globe temperatures.

Category WBGT°F WBGT°C Flag Color
1 < 82 < 27.8 White
2 82 - 86.9 27.8 - 30.5 Green
3 87 - 89.9 30.5 - 32.2 Yellow
4 90 - 92 32.3 - 33.3 Red
5 > 92 > 33.3 Black