National Weather Service United States Department of Commerce

Dangerous Heat Continues; Monitoring Excessive Rainfall and Flash Flooding

The heat continues along and east of the Mississippi River. The most significant cumulative heat impacts are expected across the Mid-Atlantic through today and eastern Ohio Valley through Friday. Severe weather and heavy rainfall potential from the Southwest, Plains, upper Midwest, Great Lakes, mid-Atlantic and Northeast the next couple of days. A disturbance near the Marianas may bring flooding. Read More >

WetBulb Globe Temperature (Prototype-Under Development. Not to be used for operational use)


The WetBulb Globe Temperature (WBGT) is a measure of the heat stress in direct sunlight, which takes into account: temperature, humidity, wind speed, sun angle and cloud cover (solar radiation). This differs from the heat index, which takes into consideration temperature and humidity and is calculated for shady areas. If you work or exercise in direct sunlight, this is a good element to monitor. Military agencies, OSHA and many nations use the WBGT as a guide to managing workload in direct sunlight.

 
 
Initial values are estimates
for the selected location
adjust sliders as needed
Month:
 
 
Day:
 
 
Latitude:
 
 
Fcst Max Temp(F):
80
 
DewPoint(F):
70
 
RH(%):
 
 
Wind Speed(mph):
 
 
Cloud Cover(%):
 
 

HeatIndex(F):
88
 
WBGT(F):
88
 

wbgt heatIndex
WetBulb Globe Temperature Heat Index

Comparison with Heat Index

 
WBGT
Heat Index
Measured in the sun
Measured in the shade
Uses Temperature
Uses RH
Uses Wind
Uses Cloud Cover
Uses Sun Angle

Examples

Temp F Dwpt F RH % Sky % Wind mph HeatIdx F WBGT F
90 65 42 05 03 92 89
90 65 42 05 13 92 83
90 65 42 65 13 92 81
90 70 52 10 06 96 88
90 70 52 60 06 96 86
90 70 52 60 13 96 85
100 70 39 10 13 108 90
100 70 39 10 5 108 94
100 70 39 65 05 108 91

 



Preparedness - What to do before doing outdoor activities when the WBGT is high -
  • Wear a hat and light weight, light fitting, light colored clothes.
  • Plan to take frequent breaks in shady areas.




  •  
  •  
  • Safety - What to do while doing outdoor activities when the WBGT is high -
  • Take breaks in the shade. Strenuous outdoor activities should be reduced, especially in direct sunlight where there is little ventilation.
  • Drink plenty of water or other non-alcohol fluids. Your body needs water to keep cool. Drink plenty of fluids even if you don’t feel thirsty.
  • Don’t get too much sun. Sunburn makes the job of heat dissipation that much more difficult
Other Resources
More WBGT Information
WBGT Research Paper
OSHA work load and WBGT Manual

 

Suggested Actions and Impact Prevention
WBGT(F)
Effects
Precautionary Actions
< 80    
80-85 Working or exercising in direct sunlight will stress your body after 45 minutes. Take at least 15 minutes of breaks each hour if working or exercising in direct sunlight
85-88 Working or exercising in direct sunlight will stress your body after 30 minutes. Take at least 30 minutes of breaks each hour if working or exercising in direct sunlight
88-90 Working or exercising in direct sunlight will stress your body after 20 minutes. Take at least 40 minutes of breaks each hour if working or exercising in direct sunlight
>90 Working or exercising in direct sunlight will stress your body after 15 minutes. Take at least 45 minutes of breaks each hour if working or exercising in direct sunlight