Welcome to the the Wet Bulb Report

Wet Bulb Report is a platform committed to educating people about the dangers of being outside in dangerously hot and humid conditions.

 

What is wet bulb globe temperature?

Wet bulb globe temperature, or WBGT, is different from heat index or "feels like" temperature. The WBGT consists of several inputs, which are as follows:

  1. The "dry bulb" temperature, which is what a normal thermometer would read in the shade.
  2. The "wet bulb" temperature, which is a thermometer with the bulb (the part you would put under your tongue) in a wet cloth.
  3. The "black globe" temperature, which is a thermometer inside a copper globe that is painted black and placed in the sun.

The dry bulb temperature is what one could consider to be a basic temperature reading. The wet bulb, on the other hand, measures the effect of evaporation on the thermometer, which cools it. However, when the relative humidity is high, this evaporation slows and reduces its cooling effect. Lastly, the black globe measures the effects of solar radiation on the temperature, which is offset by the wind cooling the globe.

Thus, high temperature combined with high relative humidity, high solar radiation, and low windspeed can produce a fatal environment where it is physically impossible to cool oneself while outdoors because even your perspiration cannot evaporate quickly enough to cool your body.

 

So I should replace my thermometer with a wet bulb global thermometer?

Not exactly. You can get localized data using instrument values from a personal weather station that we can use to substitute or extrapolate the measurements of a wet bulb globe device.

 

Who can figure out such devices?

Currently, Wet Bulb Report only supports the Ambient Weather devices that have WiFi connectivity to upload sensor data to the internet. The following models have such capabilities, and the instruments needed to derive the WBGT:

See the Ambient Weather Station comparison chart for the model that best suites your needs.
 

What should I do when the WBGT gets to risky temperatures?

Always err on the side of caution. There are many factors that impact your risk, such as the following:

  • General fitness
  • Pre-existing conditions
  • Acclimation to the environment
  • Continuous versus intermittent activities
Range (F) Range (C) Risk Work / Rest Ratio Per Hour Practice / Break Ratio Water Intake
< 82° < 27.7° None No additional breaks required
82° - 84.9° 27.7° - 29.3° Low 45 mins : 15 mins 1 pint - 1 quart per hour
85° - 87.9° 29.4° - 31° Moderate 30 mins : 30 mins 1 quart per hour
88° - 89.9° 31.1° - 32.1° High 20 mins : 40 mins
>= 90° >= 32.2° Extreme Cease all work